bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fracture behavior of poly(vinyl chloride)/methyl methacrylate/butadiene/styrene polymer blends
Authors: Takaki Akira , Hasegawa Toshihiko , Isogawa Masataka , Narisawa Ikuo 
Published: December 2004

AbstractThe fracture mode of poly(vinyl chloride)/methyl methacrylate/butadiene/styrene (PVC/MBS) polymer blends can change from ductile to brittle in accordance with the changes in shape of the test specimen or test conditions. Therefore, the mechanisms of impact energy absorption and the main cause of stress whitening are complicated. The following results on PVC/MBS blends were obtained by carrying out fracture experiments at different test speeds and temperatures:

The ductile/brittle fracture mode of the PVC and PVC/MBS blends can be explained by σ (the craze initiation stress)/σy (the shear yield initiation stress), which depends on the strain rates and temperature.
The fracture behavior of the PVC/MBS blends can be classified into the following types from the standpoints of fracture mode and whitening degree: Fracture I: ductile fracture without whitening;Fracture II: ductile fracture with whitening; andFracture III: brittle fracture without whitening.
The following concepts can be estimated from the measurements of yield stress, specific gravity and SEM, TEM and visual observations. In Fracture I, shear yield occurs mainly. In Fracture II, both shear yield and crazing occur. In Fracture III, deformation of the rubber and local crazing occur.
The main cause of stress whitening in PVC/MBS blends is light scattering by cavities in the rubber particles.
In Fracture II, at first, crazes with cavities in the rubber particles occur. Then, shear yield occurs. Finally, crazes are healed by the heat, and only the cavities in the rubber remain.
Performance blends based on recycled polymers
Authors: Akkapeddi M. K. , Van Buskirk B. , Mason C. D. , Chung S. S. , Swamikannu X. 
Published: December 2004

AbstractThe recent growth in the post‐consumer recycling of plastics presents an opportunity for developing new, value‐added blend products from the recycled polymers. However, in order to develop blends with useful performance characteristics, suitable techniques of compatibilization and impact modification must be employed. In this study, reactive toughening and compatibilization techniques have been found to be particularly useful in achieving high thermal embrittlement resistance in the blends of recycled poly(ethylene terephthalate) containing functionalized ethylene copolymers and polycarbonate. Reactive compatibilization of recycled polyolefin blends with poly(ethylene terephthalate) and polyamide has also been investigated.
Stress‐strain behavior and dynamic mechanical properties of poly(1,1‐dimethyl‐1‐sila‐cis‐pent‐3‐ene), poly(1‐methyl‐1‐phenyl‐1‐sila‐cis‐pent‐3‐ene) and of these polymers after crosslinking with sulfur
Authors: Chen Min Wei , Liao Charles X. , Weber William P. 
Published: December 2004

AbstractMechanical properties of polymers can be described by their stress/strain curves and by their behavior under dynamic mechanical thermal analysis (DMTA). The purpose of this paper is to report such mechanical properties for two unsaturated polycarbosilanes: poly(1, 1‐dimethyl‐1‐sila‐cis‐pent‐3‐ene) (I) and poly(1‐methyl‐1‐phenyl‐1‐sila‐cis‐pent‐3‐ene) (II). Tensile strength, elongation at break, modulus, bending modulus, Tg, and tan δ for I, II and for sulfur crosslinked I and II have been measured. The influence of polymer molecular weight, quantity of crosslinking agent, cure time, presence of carbon black filler, the effect of crosshead speed, and frequency on these properties was investigated.
Monomer chain cross‐transfer constants and cross termination factor evaluations on styrene‐acrylonitrile copolymerization
Authors: Mendizabal E. , Velazquez S. , Gonzalez V. , Jasso C. F. 
Published: December 2004

AbstractUsing low conversion bulk copolymerization experimental data and the apparent rate constant model, the monomer chain cross‐transfer rate constants and the cross‐termination coefficient were evaluated. It was found that the dependence of the cross‐termination coefficient on composition is a function of initiator efficiency and that monomer chain cross‐transfer rate constant are relevant for the theoretical estimation of the molecular weights and molecular weight distributions.
Comparison of microwave and thermal cure of an epoxy/amine matrix
Authors: Jordan Catherine , Galy Jocelyne , Pascault Jean‐Pierre , Moré Claude , Delmotte Michel , Jullien Henri 
Published: December 2004

AbstractAn investigation was carried out into the effect ofa microwave cure on an epoxy prepolymer with a cycloaliphatic diamine mixture, as compared to a standard thermal cure. The microwave waveguide and process (propagation mode TE01) were adjusted to obtain large homogeneous samples. The extent of reaction, x, was measured during the microwave processing by size exclusion chromatography and differential scanning calorimetry. A good estimate of x was found using a modified DiBenedetto equation correlating x and the glass transition temperature Tg. The homogeneity of the samples was checked during the last steps of cure, showing the efficiency of the microwave processing and waveguide. The influence of the nature of the mold (metallic or dielectric) on the reaction kinetic was also investigated. Samples cured by both thermal and microwave processing were characterized by dynamic and static mechanical properties and then compared with those of fully crosslinked networks, i.e., postcured at a high temperature.
Molecular weight dependence of the fracture toughness of glassy polymers arising from crack propagation through a craze
Authors: Hui C. Y. , Kramer E. J. 
Published: December 2004

AbstractWe investigate criteria for craze failure at a crack tip and the dependence of craze failure on the molecular weight of the polymer. Our micromechanics model is based on the presence of cross‐tie fibrils in the craze microstructure. These cross‐tie fibrils give the craze some small lateral load bearing capacity so that they can transfer stress between the main fibrils. This load transfer mechanism allows the normal stress on the fibrils directly ahead of the crack tip in the center of the craze to reach the breaking stress of the polymer chains. We solve for stress field near the crack trip and use it to relate craze failure to the external loading and microstructural quantities such as the craze widening (drawing) stress, the fibril spacing, the molecular weight, and the force to break a single polymer chain. The relationship between energy flow to the crack tip due to external loading and the work of local fracture by fibril breakdown is also obtained. Our analysis shows that the normal stress acting on the fibrils at the crack tip increases linearly as the square root of the craze thickness, assuming that the normal stress distribution is uniform and is equal to the drawing stress acting on the craze‐bulk interface. The critical crack opening displacement, and hence the fracture toghness is shown to be proportional to [1–(Me/qMn)]2, where Me is the entanglement molecular weight, Mn is the number average molecular weight of polymer before crazing, and q is the fraction of entangled strands that do not undergo chain scission in forming the craze.
Correlations between relaxation time spectrum and melt spinning behavior of polypropylene. II: Melt spinning simulation from relaxation time spectrum
Authors: Fulchiron R. , Michel A. , Verney V. , Roustant J. C. 
Published: December 2004

AbstractUsing an integral nonlinear constitutive equation including the Log‐Normal relaxation spectrum, the fiber‐spinning behavior of commercial polypropylenes is studied. The relaxation spectrum is strongly related to the molecular weight distribution. Moreover, by means of a finite element analysis, simulated stress and velocity profiles are obtained either in isothermal or nonisothermal cases. In the isothermal case, broadening the relaxation spectrum leads to more pronounced curvature of the velocity profile. In the nonisothermal case, the critical draw ratio is sensitive to the mean relaxation time which depends on both average molecular weight and distribution breadth. It is shown that increasing the average relaxation time leads to a less rapid growth of the velocity. Furthermore, this effect is less pronounced when the relaxation spectrum is wider.
Diffusion of butanediol in poly(butylene terephthalate) (PBT) melt and analysis of pbt polymerization reactor with surface renewal
Authors: Yoon Kwan Han , Park O. Ok 
Published: December 2004

AbstractA reactor with surface renewal, originally designed for poly(ethylene terephthalate) (PET) polymerization, was applied for poly(butylene terephthalate) (PBT) polymerization. A comprehensive model including side reactions was developed and compared with the experimental results. The diffusivity of butanediol (BD) in PBT melt was measured separately by desorption experiments (Db − 1.08 × 106 exp(−32600 / RT) (m2/min)). Optimum operating temperature for PBT polymerization was found to be around 250°C in order to avoid degradation.
A constitutive theory for polyolefins in large amplitude oscillatory shear
Authors: Giacomin A. J. , Jeyaseelan R. S. 
Published: December 2004

AbstractA versatile transient network theory has been used as a framework for the interpretation of large amplitude oscillatory behavior of polyolefin melts in terms of their entanglement kinetics. The model reasonably describes all previously published measurements of the large amplitude oscillatory shear behavior on melts. Seven polyolefins are examined, three new materials and four previously studied. A qualitative difference in the nonlinear behavior in large amplitude oscillatory shear has been identified between the polyethylenes examined and the two other polyolefins, polystyrene and polyisobutylene.
Effect of short chain branching on the viscoelastic behavior during fatigue fracture of medium density ethylene copolymers
Authors: Showaib E. A. , Moet A. , Sehanobish K. 
Published: December 2004

AbstractA method to determine viscoelastic changes in medium density polyethylene (MDPE) pipe specimens associated with the crack tip during fatigue crack initiation (FCI) and propagation (FCP) experiments is described. The load‐displacement curves are analyzed to obtain the phase angle, δ. Changes in δ are related to the number of cycles of crack initiation of three different MDPE copolymers: hexene (H), butene (B), and methyl pentene (MP) copolymers. These changes are related to craze formation and growth at the notch tip, leading to crack initiation and to the irreversible work, Wi, expended on them. Within a given material, step wise increments in δ distinguish the onset of crack initiation and the brittle‐to‐ductile transition in crack growth. The magnitudes of tan δ and Wi are noted to be in quantitative agreement with the resistance of the three copolymers to FCI and brittle propagation that rank in the order: isobutyl (MP) > ethyl (B) > butyl (H). Similar crystallinity of the three copolymers insinuates a hypothesis that variance in the nature of chain entanglements associated with the respective branch type might be accountable for the observed differences in viscoelastic character. The final stage of failure by ductile tearing is dominated by large scale plastic flow that seemingly overshadows the material differences governing time dependent brittle fracture.
Effect of mean strain on the cyclic deformation and stress relaxation in polypropylene
Authors: Ariyama Takashi 
Published: December 2004

AbstractThe influence of mean strain Changes in the range from 0 to 4% on the cyclic deformation and stress‐relaxation properties is investigated using rod specimens of polypropylene. An extensometer measures and controls the axial strain in a closed‐loop, electrohydraulic, servocontrolled mechanical testing machine. The hysteresis loop at different numbers of cycles N of N = 35, 45, and 50 are irregular in shape, and the tensile portion decreases in size as the number of cycles was increased. The stress value of the tensile portion for three mean strains of ϵm = 1.0%, 2.0%, and 4.0% remains constant, but the value of the compressive portion decreases as the mean strain was increased. The stress level at a strain width of 3% changes little with mean strain. For the strain widths of 5% and 7%, however, the minimum stress levels at N = 35, 45, and 50 increase with increasing mean strain, in contrast to the behavior of maximum stress level. The stressrelaxation tests show that the drop of stress decreases with an increase in number of cycles. The discrepancy in the results of relaxation tests is due to the effect of the difference in strain rates.
A method for measuring PVT relationships of thermoplastics using an injection molding machine
Authors: Chiu Cheng‐Ping , Liu Kuo‐Ann , Wei Jong‐Hwei 
Published: December 2004

AbstractThe objective of this study is to establish a feasible method for generating pressure‐specific volume‐temperature (PVT) data for thermoplastics on a microcomputer‐controlled injectionmolding machine (IMM). This method utilizes the injection barreel of the IMM as a pressure chamber for determining the specific volume of thermopla;stics at various pressure and temperature conditoins. An empirical equation of state based on the Tait equation s used to fit the PVT data of three resins — low‐density polythelene (LDPE), polystyrene (PS), and acrylonitrile‐butadiene‐styrene copolymer (ABS). The comparsion between LPDE's PVT data generating from the IMM and from the classical bellows method indicated that the present method can be reasonably applied for determining the specific volume of thermoplastics as a function of presure and temperature.
The effect of drawing temperature on multi‐stage drawn ultra‐high molecular weight polyethylene
Authors: Lee Dah‐Ming , Chen Wei‐Liang , Yeh Ming‐Tao , Chen Tin‐Soy 
Published: December 2004

AbstractThe effect of drawing temperature on multi‐stage drawn ultra‐high molecular weight polyethylene (UHMWE) fiber, produced by gel spinning, has been studied. Drawing at higher temperature generally gives higher crystal orientation, as expected. The activation energy of drawing increased with the draw ratio and raw 4sequence. It varied at a given draw ratio and draw stage between two temperature ranges, 85 to 115°C and 115 to 135°C. Thus, for the first draw stage, the activation energy is ∼ 19—35 KJ/Moe in the range of 85 to 115°C, and ∼ 60—99 KJ/mole in the range of 115 to 135°C. In the second stage, the activation energy is 40 KJ/mole in the range of 105 to 115°C and 70—99 KJ/mole in the range of 115 to 135°C. In the third stage, the activation energy is ∼ 92—100 KJ/mole in the range of 115 to 135°C.
Blends of thermotropic liquid crystalline polyesters and poly(butylene terephthalate): Thermal, mechanical, and morphological properties
Authors: Chang Jin‐Hae , Jo Byung‐Wook , Jin Jung‐Il 
Published: December 2004

AbstractBlends of poly(butylene terephthalate) (PBT) with three different thermotropic liquid crystalline polyesters (TLCPs) were prepared. The first TLCP (HBH‐6) consists of diad aromaticester type mesogenic units and the hexamethylene spacers along the main chain, and the second (TB‐S6) is a wholly aromatic polyester TLCP having alkoxy side groups on the terephthaloyl moiety. The last (TR‐4,6) is an LC copolymer comsisting of triad aromatic ester type mesogenic units and two differents spacers; tetramethylene and hexamethylene units. Blends of TLCP with PBT were melt spum at different LCP contents and differnt draw ratios to produce monofilaments. For the HBH‐6/PBT and TB‐S6/PBT blends, the ultimate tensile strength showed a maximum value at the 5 wt% level of LCP in the blends, and then it decreased when the LCP content was increased up to 20%. On the other hand, the initial modulus monotonically increased with increasing LCP content in all cases. The blends with TB‐S6 showed the highest tensile properties of the three blends systems. This can be ascribed to the highest rigidity of the polymer chain, which still carries relatively long alkoxy substituents that promote sufficient adhesion between the LCP and PBT matrix. When compared with the PBT fiber itself, the fibers obtained from the 5% TB‐S6/PBT blends exhibited an improvement in tensile strength by > 25% and in tensile modulus by ∼ 200%.
Factors influencing microstructure formation in polyblends containing liquid crystalline polymers
Authors: He Jiasong , Bu Wensheng , Zhang Hongzhi 
Published: December 2004

AbstractFour isotropic polymers, poly(butylene terephthalate) (PBT), polycarbonate (PC), polyethersulfone (PES) and polysulfone (PSU), were blended by extrusion with a thermotropic liquid crystalline polymer (LCP) at different temperatures. The morphology of extrudates was observed by means of scanning electron microscopy and the intrinsic aspect ratio of LCP fibrils and particles separated from matrix resin was measured with an image analysis. Special attention was paid to the LCP fibrillation in these four matrices in a wide temperature range from 270 to 360°C and the internal relations among the effects of processing parameters, such as viscosity ratio, extrusion temperature, and LCP concentration. The results show that the viscosity ratio of the dispersed LCP phase to the continuous phase is a decisive factor determining the formation of LCP fibrils, but its effect closely relates with the LCP content. In the range of viscosity ratios investigated, 0.004 to 6.9, and lower LCP content of 10%, significant fibrillation took place only at viscosity ratios below 0.01. It is predicted that the upper limit of the viscosity ratio for LCP fibrillation will increase with increasing LCP content. A comparison of the morphologies of LCP/PES blends with different LCP concentrations reveals that the LCP phase becomes continuous at a concentration of less than 50%, and high LCP content does not always favor the formation of long and uniform LCP fibrils. The extrusion temperature has a marked effect on the size of the minor LCP domains. For fibril forming systems, the percentage of LCP fibrils with larger aspect ratios increases with increasing extrusion temperatures. All these results are explained by the combined role of deformation and coalescence of the LCP disperesed phase in the blend.
The leveling of thermosetting waterborne coatings. Part IV: Effects of film thickness
Authors: Kojima Shunji , Moriga Toshinori , Takenouchi Ken 
Published: December 2004

AbstractThe influence of film thickness on the leveling of a thermosetting waterborne coating (WBC) was examined. The theory of Patton has been revised to give the proper force balance and modified to include the changes in surface tension and viscosity during leveling by the evaporation of volatile components. However, the predicted leveling process by a numerical method did not coincide with the observed results. Thus, the driving force in the theory, the hydrostatic pressure gradient in the film, was considered to be insufficient to describe the leveling process of the WBC. The hydrostatic pressure gradient can be a component of the driving force to promote leveling, but the existence of an additional component is suggested.
Rheological Study of Loosened Bulk Granular Materials
Authors: Gottschalk Jürgen 
Published: December 2004

AbstractLoosened bulk materials occur, for example, during grinding in a tube mill. Thus, a rheological study of bulk granular materials which are loosened by fluidisation should lead to a better characterization of the flow and conveying properties of the material when ground in the mill.For this measurement of fluidised bulk materials an agitating device and a rotary viscosimeter have been developed, designed and tested.First results are presented and discussed showing the fluidisation behaviour and density of the bulk material as a function of grain size as well as the flow properties as a function of the grain size and degree of fluidisation.Finally, a projection of further research work is given.
An Investigation into Capillary Hydrodynamic Chromatography
Authors: de Jaeger Nikolaas C. , Trappers Jan L. , Lardon Paul 
Published: December 2004

AbstractNow fifteen years ago, Small and co‐workers [1, 2], introduced Hydrodynamic Chromatography (HDC) as a simple method for the sizing of submicron particles. The particles are fractionated when flowing through a packed column of uniform impermeable beads and emerge in order of decreasing diameter. Noel et al. [4] and Mullins and Orr [3] reported a variant of the technique using a long open capillary tube which has been called Capillary Hydrodynamic Chromatography (CHDC).Recently Brough et al. [5] were able to expand the size range of CHDC down to particle diameters of 0.07 μm and showed that the technique is also able to achieve fractionation in organic solvents.In an attempt to obtain the same particle size analysis range with CHDC as with the recently commercialised HDC (Micromeritics), we investigated the CHDC performance in very small capillaries (0.1 and 0.15 mm). The emphasis of the study has been led on the nature and the concentration of the eluent composition. Indeed an effective reduction in capillary diameter can be obtained if one uses a commercial block copolymer as eluent material. Adsorption of the block copolymer both on the capillary wall and the particles gives rise to a sterical barrier which reduces further the effective capillary diameter and enhances the resolution of the column towards smaller particle sizes.In our view CHDC represents more possibilities in analysing real particle systems, i. e. dispersions with relatively high polymer or polyelectrolyte concentrations. For such systems classical HDC results mostly in the clogging of the column. A series of dispersions and emulsions in concentrated gelatine have been analysed and the P. S. are compared with the results obtained by LCS.
Small Angle Light Scattering Patterns from Micrometer‐Sized Spheroids
Authors: Ravey Jean‐Claude 
Published: December 2004

AbstractBy using a physical optics approximation, the scattering functions, i1 (θ), may be calculated for spheroidal particles of parameter sizes larger than 10. Emphasis is put on the angular location of their first extrema, as function of the refractive index, shape, size and orientation of the spheroid, which may greatly influence the outlook of their small angle 2 D patterns.
The Use of Calibration Techniques for the Development and Application of Optical Particle Sizing Instruments
Authors: Hemsley D. J. , Yeoman M. L. , Bates C. J. , Hadded O. 
Published: December 2004

AbstractThis paper describes seven different methods of calibrating optical particle sizing instruments based on single particle scattering theory. The results presented were obtained from a Laser Doppler Anemometer (LDA) using two concentric probe volumes of different diameters and colours. Measurements of the Doppler signal frequency, amplitude and visibility can yield the absolute particle size and velocity of individual particles providing that the optics and processor are correctly designed and implemented.The requirements for signal processing without validation bias are discussed together with the use of a Doppler signal generator for testing the processor. Calibration of the system is then described using a scanning pinhole unit, calibration plate and aerosols of bronze spheres. The other techniques described are the use of glass spheres mounted on thin stalks, Berglund‐Lui monodisperse particle generator and latex spheres entrained in a recirculating cell. The discussion indicates the sizing range over which the above techniques are applicable. This covers a total size range from 1 micron to 1 millimetre.