bluuebunny/crossref_metadata_2025_split huggingface dataset:
Carbon black filled PET/PMMA blends: Electrical and morphological studies
Authors: Mallette J. G. , Márquez A. , Manero O. , Castro‐Rodríguez R. 
Published: April 2004

AbstractIn this work, the electrical and morphological properties of blends of poly(ethylene terephthalate) (PET), poly(methyl methacrylate) (PMMA), and carbon black (CB) were analyzed. Resistivity decreases similarly in both PET and PMMA with CB concentration. Similarly in the PET/PMMA blend, extensive modification to this behavior occurs, since resistivity becomes a function of morphology and specific location of CB in the polymers. A minimum in the resistivity of the blend with 5% CB (PET basis) is observed at 100% PET, whereas with an increase in the CB content to 20%, the minimum in the resistivity shifts to 60% PET. High conductivity is observed when PET is the continuous phase (having the larger viscosity). Large stresses lead to a large dispersion of CB and a high deformation and rupture of the dispersed PMMA phase. This situation itself promotes an increase of surface area of droplets and high CB concentrations at the interface. Consideration is given to models that predict a selective location of conductive particles in the PET matrix based on its lower interfacial tension with CB.
Long chain branching and polydispersity effects on the rheological properties of polyethylenes
Authors: Hatzikiriakos Savvas G. 
Published: April 2004

AbstractThe rheological behavior of linear, and branched polyethylenes is studied as a function of the weight average molecular weight (Mw) and its distribution (MWD) as well as the level of long chain branching in an attempt to identify correlations between long chain branching, polydispersity and rheological properties. It is found that a need for vertical shift of the viscoelastic moduli data to obtain the master curves using the time‐temperature superposition principle is associated with the existence of long chain branching in the structure of the polymer. The degree of vertical shift is found to correlate with the level of long chain branching. This correlation corroborates with the observation that long chain branching correlates with the horizontal flow energy of activation. Plots of atan(G″/G′) vs. G* (known as Van Gurp plots) also reveal some important features that can be used as signs of specific features in the structure of polymers. More specifically, the area included below the Van Gurp curves correlates with the level of long chain branching and polydispersity index. The correlations are presented in graphical form and they can be used to associate rheological properties with the presence of long chain branching and/or polydispersity.
Preparation and characterization of biaxially oriented films from polybutylene terephthalate based thermoplastic elastomer block copolymers
Authors: Li Hang , White James L. 
Published: April 2004

AbstractFilm casting and biaxial stretching of a series of polyester thermoplastic elastomers (TPEs) were studied. Biaxial orientation in the stretched films was characterized by wide‐angle X‐ray diffraction and birefringence measurements. Biaxial orientation factors were determined. The X‐ray diffraction and birefringence clearly indicated the development of planar biaxial orientation in the stretched films with biaxial stretching. The phenyl groups in the stretched PBT and TPE films gradually became more parallel to the film surfaces with increasing biaxial orientation. The lower the PBT content in the stretched TPE films, the lower the planar biaxial orientation achieved. The β form of crystalline PBT was found only in the stretched PBT films, but not in the TPE films.
Influence of residual stress on the relationship between pipe pressure and C‐ring tests
Authors: Whittle A. J. , Burford R. P. , Hoffman M. J. 
Published: April 2004

AbstractThe effects of residual stress in modified poly(vinyl chloride) pipes upon the relationship between pressure tests and C‐ring tests have been studied. A series of pressure tests were carried out at different hoop stresses using both fixed‐end and free‐end enclosures. The C‐ring test was used to determine the yield strength of the material as a function of time. The difference in behavior between the fixed end and free end configurations was less than predicted by the von Mises analysis assuming the only stresses in the pipe wall were generated by the applied internal pressure. Both configurations produced lower results than predicted on the basis of the C‐ring tests. The residual stresses in the hoop and longitudinal directions were measured. Taking into account the residual and applied stresses, the von Mises criterion for yield was used to calculate the uniaxial yield stress of the material for both end enclosure configurations. The results were similar to the yield stress measured in uniaxial tension. The von Mises criterion for yield has been shown to provide an acceptable method of analysis of pressure tests with fixed and free end enclosures and the C‐ring, when residual stress is taken into account.
Yield modeling of an aliphatic polyketone terpolymer in multiaxial stress states
Authors: Kartunen Nicole R. , Lesser Alan J. 
Published: April 2004

AbstractA continuum yield model for pressure dependent anisotropic materials that accounts for the stress state has been combined with a thermally activated model to account for the temperature and rate dependence of yield stress. The resulting model has been applied to describe the yield behavior of a semicrystalline aliphatic polyketone terpolymer. Utilizing biaxial data from this thermoplastic, best‐fit values for loading along principal directions were determined. With these principal values, predictions for the yield strength under biaxial loading conditions were made. These predictions have been compared to experimental data obtained from the material at four different temperatures and three different strain rates. The experimental and theoretical results appear to compare quite well with each other.
Degradation of poly(methyl methacrylate) (PMMA) with aluminum nitride and alumina
Authors: Lee Yi‐Mu , Viswanath Dabir S. 
Published: April 2004

AbstractThis paper deals with the thermal and thermal‐oxidative degradation of pure poly(methyl methacrylate) (PMMA), PMMA/A1N and PMMA/Al2O3 composites. Kinetic parameters were determined from the weight loss data using non‐isothermal Thermogravimetric Analysis (TGA). The amount and morphology of the carbon residue in the burnt samples under N2 and air atmospheres were also investigated using a Leco combustion analyzer. This study also showed that the normally accepted three‐stage polymer thermal degradation, and hence three regions of Arrhenius linearity, can be treated with one value of activation energy. This is a basic departure from the normally accepted three different regions and applying the same diffusion equation (such as Jander diffusion) separately to each region. In nitrogen atmosphere, the activation energy of pure PMMA was 129.4 kJ/mol; however, the activation energies of 14% PMMA/AlN and PMMA/Al2O3 were found to be 119.5 and 118.2 kJ/mol, respectively.
Polymer blend de‐mixing and morphology development of immiscible polymer blends during tube flow
Authors: Karami Askar , Balke Stephen T. 
Published: April 2004

AbstractThis work is an investigation of morphology and de‐mixing of polymer blends during melt flow through a tube. Morphology is the relative size, shape and location of each distinguishable phase present in a polymer blend. De‐mixing is the shear‐induced migration of different types of polymers away from each other during the flow. The ability to tailor de‐mixing during extrusion can potentially result in a new family of plastics waste recycling processes with mixed waste entering an extruder and separate streams of different polymer types leaving it. Also, control of morphology development can lead to the formation of layered structures without the need for two or more extruders and co‐extrusion. This work is directed at elucidating morphology development and de‐mixing of polymer blends in the most simple process design: melt flow through a tube. Shear‐induced migration was quantitatively shown in various polyethylene‐polypropylene, polypropylene‐nylon 6 and polyethylene‐nylon 6 blends. The migration observed was in accord with the hypothesis that the system tends to minimize its rate of energy dissipation for a fixed flow rate. The ratio of the viscosity of the dispersed phased to that of the continuous phase greatly influenced the morphology of polypropylene‐nylon 6 and polyethylenenylon 6 blends: a droplet‐dispersed phase structure occurred at a high viscosity ratio, whereas a multi‐layer structure resulted at viscosity ratios near unity. Shear‐induced deformation and coalescence contributed to formation of the multi‐layer structure.
The effects of PC‐PMMA block copolymer on the compatibility and interfacial properties of PC/SAN blends
Authors: Kang E. A. , Kim J. H. , Kim C. K. , Oh S. Y. , Rhee H. W. 
Published: April 2004

AbstractBlock copolymers of polycarbonate (PC) and polymethylmethacrylate (PMMA), PCb‐PMMA, were examined as compatibilizers for blends of PC with styrene‐co‐acrylonitrile (SAN) copolymer. PC‐b‐PMMA was added to blends of PC with SAN containing various amounts of AN. The average diameter of the dispersed particles was measured with an image analyzer, and the interfacial properties of the blends were analyzed with an imbedded fiber retraction (IFR) test and an asymmetric double cantilever beam fracture test. The average particle size and interfacial tension of the PC/SAN blends reached a minimum value when the SAN copolymer contained about 24 wt% AN. A maximum in the adhesion energy was also observed at the same AN content. Interfacial tension and particle size were further reduced by adding PC‐b‐PMMA to the PC/SAN blends. Fracture toughness of the blends was also improved by enhancing the interfacial adhesion by the addition of PC‐b‐PMMA. The addition of PC‐b‐PMMA copolymer was more effective at improving the interfacial properties of PC/SAN blends than was varying the AN content of the SAN copolymers. The interfacial properties of the PC/SAN blends were optimized by adding a block copolymer and using an SAN copolymer that had minimum interaction energy with PC.
Non‐isothermal crystallization and multiple melting behavior of syndiotactic polystyrene—pre‐melting temperature effects
Authors: Chiu Fang‐Chyou , Peng Chi‐Gong , Fu Qiang 
Published: April 2004

AbstractThis work investigated how pre‐melting temperature (Tmax) and cooling rate (C) affected the non‐isothermal melt crystallization, melting behavior and crystal structure of syndiotactic polystyrene (sPS) by using differential scanning calorimetry (DSC) and wide angle X‐ray diffraction (WAXD) techniques. Experimental results indicated that raising Tmax or C decreased the crystallization peak temperature (Tp) and crystallization initiating temperature (Ti). The crystallization kinetics was analyzed through the Ozawa equation. Although the Ozawa exponent n and cooling function K(T) were determined for Tmax = 340°C and Tmax = 315°C specimens, for Tmax = 290°C specimens, the Ozawa equation was not applicable. Activation energies for the non‐isothermal crystallization processes of different Tmax specimens were estimated to be approximately 418 kJ/mol. As Tmax was raised the nucleation rate of sPS became slower. The multiple melting peaks were associated with different polymorphs as well as recrystallized crystals that formed during heating scans. The percentage content of α polymorph formed in the crystals under various crystallization conditions was estimated through WAXD experiments.
Creep modeling of ABS pipes at variable temperature
Authors: Lu J. P. , Burn L. S. , Tiganis B. E. 
Published: April 2004

AbstractOne of the characteristic behaviors of plastic (or viscoelastic) materials is the creep phenomenon, which is defined as the continuing deformation under a constant load with time. Although research on creep of plastic pipes has been widely carried out in other plastics, little work has been reported for creep in ABS (acrylonitrile‐butadiene‐styrene) pipes at high temperatures. In this paper, the generalized Kelvin series of formulae, which consists of six Kelvin elements, a power model, as well as logarithmic regressions, are applied to the experimental data measured from creep tests under constant bending stresses at different temperatures for two ABS resins. The least‐squares method was used to adjust the Kelvin model parameters, and a Levenberg‐Marquardt non‐linear least‐squares regression procedure was used to determine the creep parameters in the power model. This led to empirical formulae for creep compliance defined as the reciprocal of the creep modulus. This creep modulus can provide a means to evaluate the long‐term structural properties for different resins used in pipe production.
Evaluation of three methods for the measurement of crystallinity of pet resins, preforms, and bottles
Authors: Bashir Z. , Al‐Aloush I. , Al‐Raqibah I. , Ibrahim M. 
Published: April 2004

AbstractThe control of crystallization is important at all processing stages of the PET bottle industry, from the manufacture of bottle resins to the fabrication of preforms and bottles. In this work, we sought to evaluate critically three methods of crystallinity measurement. We have used density, Differential Scanning Calorimetry (DSC), and Modulated Differential Scanning Calorimetry (MDSC) to study the crystallinity of PET chips, preforms, and bottles. The accuracy, precision, and general validity of each technique and the problems of interpretation are discussed.
A simulation of the non‐isothermal resin transfer molding process
Authors: Antonucci Vincenza , Giordano Michele , Nicolais Luigi , Di Vita Gandolfo 
Published: April 2004

AbstractA simulation of the non‐isothermal resin transfer molding manufacturing process accounting for both the filling and the consolidation stage has been developed. The flow of an exothermally reactive resin through a porous medium has been analyzed with reference to the Darcy law, allowing for the chemorheological properties of the reacting resin. Thermal profile calculations have been extended to a three phase domain, namely the mold, the dry preform and the filled preform. The mold has been included in order to evaluate the thermal inertial effects. The energy balance equation includes the reaction term together with the conductive and convective terms, and particular attention has been devoted to setting the thermal boundary condition at the flow front surface. The moving boundary condition has been derived by a jump equation. The simulation performance has been tested by comparing the predicted temperature profiles with experimental data from literature. Further numerical analysis assessed the relevance of using the jump equation at the flow front position for both filling time and thermal profile determination.
Processing behavior of polycarbonate/functionalized‐ethylene copolymer blends
Authors: Dias Marcos L. , Fernandes Maria Josumitra A. 
Published: April 2004

AbstractThe melt blending of polycarbonate (PC) and ethylene‐methacrylic acid copolymers (EFC) either in the acid form (EFC‐H) or partially neutralized with sodium (EFC‐Na) or zinc (EFC‐Zn) was investigated. Torque monitoring of the blending showed that the polymers are capable of reacting generating new chemical species that increase the melt viscosity. As general behavior, the torque curves pass by a maximum that takes place before 30 min, the final torque being higher than that of the individual polymers. SEC analyses reveal that PC degradation also occurs and is stronger in the case of blends with EFC‐Na that acts to catalyze PC degradation, promoting CO2 formation. FTIR studies on chloroform insoluble fractions of the PC/EFC‐Zn blends showed that in addition to a very small number of carbonate groups, feature absorption bands of aromatic ester and hydroxyl groups appear in the new chemical species formed during the reactive processing.
Thermo‐chemical response of vinyl‐ester resin
Authors: Stone M. A. , Fink B. K. , Bogetti T. A. , Gillespie J. W. 
Published: April 2004

AbstractThis paper presents the thermo‐chemical characterization of Dow Derakane 411‐C50 commercial vinyl‐ester resin at low temperatures (20°C to 40°C). Differential Scanning Calorimetry (DSC) and Torsional Braid Analysis (TBA) are the experimental techniques used to characterize the material behavior. The cure kinetics are studied using DSC and are modeled using a modified autocatalytic equation with a maximum degree‐of‐cure term. Also, the effect of inhibitors in the resin system is accounted for by an inhibitor depletion model. The glass transition temperature (Tg) is also characterized using TBA and related to the degree of cure. It was found that the Tg and the degree of cure do not exhibit a linear relationship for this resin system. The findings presented in this work provide information for accurate cure modeling and process simulation of vinyl‐ester materials.
Analysis of the isothermal mechanical response of a shape memory polymer rheological model
Authors: Bhattacharyya A. , Tobushi H. 
Published: April 2004

AbstractIn this paper, we derive the isothermal mechanical response of a 4‐element rheological model for shape memory polymers (SMP) in the context of (i) constant stress, (ii) constant strain, (iii) constant stress rate, (iv) constant strain rate, (v) periodic strain. The effect of shape memory strain (modeled by a friction element) and the temperature dependence of the material properties on the SMP response are examined for a polyurethane shape memory polymer of the polyester polypole series. In particular, it is possible to identify a threshold frequency during periodic loading, near which the damping capacity of the SMP is strongly affected by an increasing shape memory strain. On the other hand, when the applied frequency is much greater than the threshold value, an increasing shape memory strain ceases to have any effect on the damping. It is also shown that at a given frequency (significantly greater than the threshold value), the damping capacity as a function of temperature attains a maximum. While this maximum value is frequency‐dependent (being inversely proportional), the temperature at which the maximum is attained is frequency‐independent, and is analytically shown to be the glass transition temperature.
Biodegradable polymer blends of poly(L‐lactic acid) and gelatinized starch
Authors: Park Jun Wuk , Im Seung Soon , Kim Soo Hyun , Kim Young Ha 
Published: April 2004

AbstractGelatinized starches were prepared with various content of glycerol and were investigated in terms of the effect of the glycerol addition on characteristics of starch and its blends. Poly (L‐lactic acid) (PLA) with various ratios of linear/star shaped PLA and starch gelatinized with various ratios of water/glycerol were melt‐blended by using twin screw mixer. The blends were characterized by DSC thermal analysis, tensile test and morphological analysis. Gelatinization of starch was found to lead to destruction or diminution of hydrogen bonding in granules and a decrease of crystallinity of starch. DSC data showed that starch played a role as a nucleating agent and glycerol as plasticizer contributed to an improvement in crystallinity in PLA blends. When the content of starch increased, the size of spherulites in PLA blends was smaller and less regular. In the case of PLA/pure starch blends, the voids appeared, which were formed by the separation of starch particles from the matrix. But for PLA/gelainized starch blends, these voids were not observed. In the case of blends with linear PLA and starch gelatinized with water/glycerol ratio of 100/40, the greatest superiority of mechanical properties was shown and the toughness was improved compared with PLA/pure starch blends.
Effect of strain rate on the fracture toughness of some ductile polymers using the essential work of fracture (EWF) approach
Authors: Ching Emma C. Y. , Poon Wendy K. Y. , Li Robert K. Y. , Mai Yiu‐Wing 
Published: April 2004

AbstractThe plane strain fracture toughness of two ductile polymers, ultra high molecular weight polyethylene (UHMWPE) and acrylonitrile‐butadiene‐styrene (ABS), was measured by using the essential work of fracture approach. Truly plane strain fracture toughness (wIe) was measured for ABS at quasi‐static and impact rates of loading. For UHMWPE, the measured values were only “near” plane strain values (wIe*). It was confirmed both wIe* and wIe were independent of specimen type but dependent on strain rate. For UHMWPE, there was a negative strain rate effect, i.e., wIe* decreased with increasing loading rate. At low quasi‐static loading rate (v = 10 mm/min), wIe* was constant at 55 kJ/m2. It then decreased to 15 KJ/m2 when the loading rate was increased to 100 mm/min, and remained at that value even up to impact rate of loading (v = 3.7 m/s). For ABS, a mild positive strain rate effect was observed. wIe increased from 13 kJ/m2 at v = 10 mm/min to 17 kJ/m2 at v = 3.7 m/s.
A study of the effect of PP‐g‐MA and SEBS‐g‐MA on the mechanical and morphological properties of polypropylene/nylon 6 blends
Authors: Tucker J. David , Lee Sunggyu , Einsporn Richard L. 
Published: April 2004

AbstractThe mechanical and morphological properties of polypropylene/nylon 6 blends compatibilized with PP grafted with maleic anhydride (PP‐g‐MA) and styrene/ethene‐co‐butene/styrene grafted with maleic anhydride (SEBS‐g‐MA) are studied using a special version of a factorial design known as extreme vertices. Properties examined include yield stress, modulus, elongation, toughness, impact strength and morphology. Comparisons are made between various treatment combinations (i.e. a variety of blends) and polypropylene homopolymer using various statistical methods including analysis of variance (ANOVA). Scheffe's Test and Duncan's Multiple Range Test. Significant differences were found for yield stress, modulus, elongation, toughness and impact strength for specific treatment combinations versus PP as well as on average. Ternary diagrams are used to plot response surfaces of the measured data illustrating the main effects and interactions involved, while allowing correlations to be made with blend morphology. Indications from test results and analysis of response surfaces show a strong relationship between nylon/compatibilizer ratio and mechanical properties.