bluuebunny/crossref_metadata_2025_split huggingface dataset:
Electrodeposition of BTDA‐ODA‐PDA polyamic acid coatings on carbon fibers from nonaqueous emulsions
Authors: Chen Yan , Iroh Jude O. 
Published: April 2004

AbstractElectrochemical deposition of polyamic acid copolymer of 3,3′,4,4′‐benzophenonetetracarboxylic dianhydride (BTDA), 4,4′‐oxydianiline (ODA) and 1.3‐phenylenediamine (PDA) was performed from a nonaqueous emulsion on carbon fibers. The electrodeposited PAA was subsequently dried. The yield and quality of deposited polyamic acid are strongly dependent upon a number of parameters that are related to the formulation and characteristics of polyamic acid emulsion. These parameters include solvent/precipitant ratio, concentration of surfactant, and solids content. The deposition yield of PAA was related to the applied current density, deposition time, and the charge passed, and was found to obey Faraday's laws of electrolysis. The coulombic efficiency was calculated.
Impact fatigue of a polycarbonate/acrylonitrile‐butadiene‐styrene blend
Authors: Ho Ming‐Hsiung , Hwang Jiun‐Ren , Doong Ji‐Liang , Fung Chin‐Ping 
Published: April 2004

AbstractThis study analyzes the impact properties of a polycarbonate/acrylanitrile‐butadiene‐styrene (PC/ABS) blend. The specimens were prepared under various injection molding conditions, including filling time, melting temperature, and mold temperature. Impact tests were performed with a Dynatup drop weight impact tester at different impact energies (10, 15, 20, 25 J). The fracture mechanism was examined with a scanning electron microscopy. The results indicated that the load‐time history of the PC/ABS blend has approximately a sinusoidal form in impact. The best injection molding conditions are a filling time of 12 s, a melting temperature of 260°C and a mold temperature of 80°C. In this case, the specimen shows the highest energy absorbed in single impact, together with the highest impact number in impact fatigue. The impact number and the accumulation energy seem to follow an exponential curve as the impact energy decreases. The PC/ABS blend material clearly exhibited ductile fracture with a continuous reduction in strength by viscoplastic deformation. The higher the impact number, the higher the accumulation energy. The accumulation energy of impact fatigue with impact energy 10 J is about 35–45 times greater than the energy absorbed in single impact. Tearing, shear fracture, and plastic deformation are the major fracture mechanisms of the PC/ABS blend matrix in single impact and repeated impact conditions.
High temperature thermal analysis characterization of honeycomb core
Authors: Shafizadeh J. E. , Seferis J. C. 
Published: April 2004

AbstractOne of the most important processing operations in the fabrication of honeycomb composite structures is the forming of the honeycomb core. High performance honeycomb structures must be precisely formed, or contoured, in order to meet the strict dimensional specifications required by the end user of the core. However, in the composites industry today, there is no basic understanding of the high temperature behavior of honeycomb materials, which is fundamental to understanding the commercial processing of honeycomb composite structures. In this study, the thermal and mechanical responses of Nomex®‐based honeycomb core were investigated and characterized through thermal analysis. In the ribbon direction of the core, specific post‐cure temperatures were identified where the honeycomb core displayed a maximum degree of creep. In the expanded direction of the honeycomb, the core displayed no maximum‐creep temperature. This behavior was attributed to the degradation of the node adhesive. A honeycomb creep time constant (τc) was also defined and evaluated as a function of the honeycomb post‐cure temperature. From this analysis, the softening of the dip resin was determined to play a larger role in creeping and deforming the core than the mechanical properties of the Nomex substrate.
Comparison of crystallization kinetics of miscible blends of syndiotactic polystyrene with atactic polystyrene or poly(1,4‐dimethyl‐p‐phenylene oxide)
Authors: Wu Fu Sun , Woo E. M. 
Published: April 2004

AbstractCrystallization kinetics were characterized by using isothermal differential scanning calorimetry (DSC) analysis on neat semicrystalline syndiotactic polystyrene (s‐PS) and its miscible blends with atactic (amorphous) polystyrene (a‐PS) or with poly (1,4‐dimethyl‐p‐phenylene oxide) (PPO). The crystallization behavior of neat s‐PS polymer was compared to its miscible blends. The results suggest that the crystal growth in melt‐crystallized s‐PS is nearly of homogeneous nucleation and that the growth pattern of the spherulites is 3‐D spherical. The s‐PS component in its miscible blends was found to crystallize with similar behavior to that of neat s‐PS, but with lower Avrami exponents, suggesting that the nucleation mechanism is likely more heterogeneous with blending.
Non‐contacting tension measurement for molten films
Authors: Bian Baigui , Co Albert 
Published: April 2004

AbstractA novel air‐nozzle system was developed to perform non‐contacting measurement of film tension in molten films. The measurement is based on correlation between the film tension and the pressure drop across the gap from the nozzle tip to the film. Films with higher tension exhibit less deflection by the impinging air jet and, consequently, produce a higher pressure drop across a smaller gap. The correlation between film tension and pressure drop was obtained with solid films at room temperature. A procedure was developed to extend the correlation to higher temperatures. The correlation was also found to agree with film tension versus pressure drop data obtained from specially designed molten film experiments. The capability of the system was demonstrated in the film casting of a linear low‐density polyethylene melt and a low‐density polyethylene melt. Tensions in the molten films were measured at various values of draw ratio and extrusion speed.
In‐situ generation of polyamide‐6 fibrils in polypropylene processed with a single screw extruder
Authors: Li Xuedong , Chen Mingcai , Huang Yuhui , Cong Guangmin 
Published: April 2004

AbstractPolypropylene(PP) and polyamide6(PA6) were extruded with a single screw extruder. It was found that when PA6 was in the dispersed phase, it could deform and fibrillate in the PP matrix in the shear force field generated by the rotating screw. Dynamic mechanical analysis and mechanical tests showed that the mechanical properties, such as the tensile strength, impact strength, and modulus, were different in the different processing directions. With the addition of PP‐g‐MAH as a compatibilzer, the number of fibrils decreased and the dimension of the dispersed phase decreased significantly. This indicated that the compatibility has a strong effect on the in‐situ fibrillation.
In situ formation and processing of ultra high molecular weight polyethylene blends into precursors for high strength and stiffness fibers
Authors: Whitehouse C. , Liu M. L. , Gao P. 
Published: April 2004

AbstractWe present a novel process for the manufacture of ultra high molecular weight polyethylene precursors which can be subsequently made into high‐stiffness, high‐strength fibers or films. This process combines solid‐state extrusion and an in situ constrained solvent swelling process into a single stage for precursor preparation. The precursors produced by this process are shown to be highly ductile and porous. The inclusion of a small quantity of nontoxic solvent (10 wt% mineral oil) in the process has also been shown, using DSC and SEM characterization techniques, to provide the following process advantages: (i) better interfacial cohesion, because of the enhanced chain mobility at the particle surface due to the solvating effects; (ii) improved processability; and (iii) more uniform thermal properties and morphology across the extrudates due to enhanced heat transfer.
Control of part weight in injection molding of amorphous thermoplastics
Authors: Kamal Musa R. , Varela Alfredo E. , Patterson W. Ian 
Published: April 2004

AbstractTwo methods are proposed for the control of part weight in injection molding. In the PT method, part weight control is achieved by controlling the temperature and pressure of the melt in the cavity at gate freeze time. This time is considered to occur when the cavity melt pressure starts to decrease from its peak value. For the purposes of control, the bulk melt temperature is estimated from measurements by surface thermocouples at strategic locations in the cavity. A cascade scheme is implemented for the control of bulk temperature from cycle to cycle. A self‐tuning algorithm, with an observer, is employed for controlling the cavity pressure‐time profile, to follow a set point trajectory during a cycle. In PWT control, the coolant temperature is controlled, while the peak cavity pressure is adjusted in a given cycle to compensate for bulk melt temperature deviations measured in the previous cycle. Both PT and PWT control reduce variance in part weight. PWT control appears to yield the best results.
Thermoplastic elastomers based on ionomeric polyblends of zinc salts of maleated polypropylene and maleated EPDM rubber
Authors: Antony Prince , Bandyopadhyay S. , De S. K. 
Published: April 2004

AbstractIonomeric polyblends of the zinc salt of maleated EPDM rubber (Zn‐mEPDM) and the zinc salt of maleated polypropylene (Zn‐mPP) in the composition range from 90/10 to 60/40 wt% behave as ionic thermoplastic elastomers (ITPE), which show synergism in physical properties. The ionomeric polyblend shows higher physical properties than the corresponding non‐ionomeric polyblend. Infrared spectroscopy reveals the occurrence of intermolecular ionic interactions between the component ionomers in the blend. Zinc stearate acts as a platicizer in the melt of the ionomeric polyblend, which exhibits a higher melt viscosity than the corresponding non‐ionomeric polyblend. The blend can be reprocessed like a thermoplastic, with no drop in strength even after three extrusion cycles.
Reactive compatibilization of polypropylene/polyethylene terephthalate blends
Authors: Champagne Michel F. , Huneault Michel A. , Roux Claudine , Peyrel Wilfried 
Published: April 2004

AbstractThe reactive compatibilization of polypropylene/polyethylene terephthalate (PP/PET) blends by addition of glycidyl methacrylate grafted PP (PP‐g‐GMA) was studied. Two PP‐g‐GMA copolymers, containing either 0.2 or 1.2 wt% of GMA, were used as interface modifiers. These were incorporated into PP blends (with either 70 or 90 wt% PET), replacing 1/5 of PP in the system. The use of these modifiers changed the blends' tensile mechanical behavior from fragile to ductile. Blend tensile strength was improved by 10% and elongation at break showed 10 to 20‐fold increases while stiffness remained constant. Scanning electron micrographs showed the PP average domain size in injection molded specimens to decrease to the micron/sub‐micron size upon addition of the GMA modified resins, while the unmodified blends exhibited heterogeneous morphology comprising large lamellae 10–20 μm wide. The low‐GMA graft content PP seemed slightly more efficient than the high GMA content PP in emulsifiying PP/PET blends. The GMA grafting level on PP had very limited effects on the blends' mechanical behavior in the range of GMA graft density provided by the two modified resins investigated.
Effect of sodium oleate addition on the morphology of polypropylene‐co‐polyamide blends
Authors: Tsebrenko M. V. , Rezanova N. M. , Nikolaeva A. P. , Tsebrenko I. A. , Lazar I. A. 
Published: April 2004

AbstractThe influence of sodium oleate additives on processing and morphology of polypropylene ‐ co‐polyamide (PP/CPA) mixture melts has been investigated. It is shown that sodium oleate is located in the interphase of the components and acts at small additives (up to 3 wt%) as an interfacial tension agent, improving miscibility of polymers, and increasing the kinetic stability of mixtures and the degree of PP dispersion in the co‐polyamide matrix. The plasticizing effect on mixture melt was observed at 7 wt% sodium oleate as a reduction of mixture viscosity. The ultrathin PP fibers (microfibers) strictly oriented in the direction of extrusion are the main type of structure produced during extrusion of a PP/CPA mixture. Addition of sodium oleate changed the PP fiber‐formation in the CPA matrix: the total number of fibers increased, their diameter and diameter distribution decreased.
Blends of thermoplastic polyurethane and maleic‐anhydride grafted polyethylene. I: Morphology and mechanical properties
Authors: Pötschke Petra , Wallheinke Katrin , Stutz Herbert 
Published: April 2004

AbstractThermoplastic polyurethane elastomers (TPU) and polyethylene (PE) form immiscible blends with an extremely low compatibility. In order to improve the dispersion, stability, and properties of these blends, polyethylene was grafted with maleic anhydride (PE‐g‐MA). Subsequently, it was blended with a commercial polyester ‐ type TPU in a twin‐screw extruder. With PE‐g‐MA as blend component, the particle size was dramatically reduced in comparison with PE. Coalescence was significantly reduced and the increase in particle size with composition was less pronounced than in blends with PE. In addition, the phase adhesion and the mechanical properties were improved by using PE‐g‐MA as minor component. Grafting of the MA onto the PE leads to a decrease of the molecular weight, the melt viscosity, and the mechanical properties of the pure PE. Hence, the reactive blend system exhibits a lower viscosity ratio. Comparison of these results with those from uncompatibilized blends with different viscosity ratios revealed that the reduction in viscosity ratio has a big influence on the blend morphology and because of that on the mechanical properties. In addition, there is a further effect on morphology and properties caused by the reduction in interfacial tension, which results from the compatibilizer formed at the interface.
Mechanical behavior of injection‐molded polystyrene/polyethylene blends: Fracture toughness vs. fatigue crack propagation
Authors: Bureau M. N. , Di Francesco E. , Dickson J. I. , Denault J. 
Published: April 2004

AbstractBlends of polystyrene and polyethylene (PS/PE), including belnds in which a styrene/ethylene‐butylene/styrene (SEBS) terpolymer was employed as a compatibilizer, were studied. Their rheology showed that the effect of the addition of SEBS to PS/PE blends was strongly affected by the blend composition and the shear rates involved in the blending and post‐forming processes. The addition of PE to PS led to a reduction of fracture toughness compared with that of PS. This effect was attributed to the fine minor phase morphology of the blends obtained after extrusion blending and injection molding. The fatigue crack propagation (FCP) results showed that the fatigue crack growth rates were significantly reduced at low and moderate range of stress intensity factor (ΔK) by the presence of PE. Performance was enhanced when SEBS was present. The results also showed that both the fracture toughness and the FCP behavior of the blends were strongly dependent on the loading direction, the minor phase morphology, the composition of the blend, and, to a lesser degree, the presence of a compatibilizer. This study demonstrates that the fracture toughness and the FCP performance of such polymer blends can vary inversely.
Mathematical modeling and experimental studies of twin‐screw extrusion of filled polymers
Authors: Kalyon Dilhan M. , Lawal Adeniyi , Yazici Rahmi , Yaras Piraye , Railkar Sudhir 
Published: April 2004

AbstractExtrusion of filled polymer is commonly employed in diverse industries including compounding operations. The analysis of extrusion of filled polymers is complicated especially by the ubiquitous viscoplasticity and wall slip of the filled polymers. Furthermore, the role played by entrainment of air in the processor, the continuously evolving microstructure, and hence the rheological behavior of the filled polymer in the mixing volume of the extruder and the flow instabilities associated with the converging flows involving the filtration of the binder polymer present additional challenges to the analysis. Specialized techniques are also necessary to quantitatively describe the dispersive and the distributive degree of mixing of the compound. The principal tasks of this study included the collection of experimental data from twin‐screw extrusion using an instrumented and industrial‐scale co‐rotating extruder in conjunction with a well‐characterized filled polymer, which exhibits viscoplasticity and wall slip. The process allowed the adequate mixing of the ingredients and the removal of its air content. Next, the processing data were compared with the results of numerical simulation using the Finite Element Method. The predictions compared favorably with the experimental temperature and pressure distributions obtained under different sets of operating conditions. The distributive degree of mixing (spatial homogeneity) of the filled polymer upon exit from the die was also characterized employing a wide angle X‐ray diffraction technique in spite of the amorphous nature of both the filler and the binder polymer, i.e., hollow glass spheres and poly(dimethyl siloxane) polymer.
Effects of nucleating agent and processing conditions on the mechanical, thermal, and optical properties of biaxially oriented polypropylene films
Authors: Yuksekkalayci Celal , Yilmazer Ulku , Orbey Nese 
Published: April 2004

AbstractThe effects of nucleating agent, temperature of crystallization, and degree of machine direction (MD) orientation on the mechanical, optical, and thermal properties of biaxially oriented polypropylene (BOPP) films were investigated. Addition of nucleating agent improved only the initial tear resistance in the MD; however, the other mechanical and optical properties did not change appreciably. In the set of experiments in which the crystallization temperature was increased, the degree of crystallinity also increased. Thus, Young's modulus, yield stress, and tensile strength increased in both directions with higher degree of crystallinity. The yield strain did not change significantly, but the strain at break was higher. Although the initial tear resistance was smaller in both directions with increasing crystallization temperature, the tear propagation resistance did not change. In this case, haze and diffuse transmittance were slightly higher, but the total transmittance was constant. In the set of experiments in which the machine direction orientation was increased, the degree of crystallinity also became higher. Owing to the effects of higher crystallinity and higher MD orientation, the modulus, yield stress, and tensile strength increased, but the yield strain and tear propagation resistance did not significantly change in both directions.
Optical monitoring of polypropylene injection molding
Authors: Thomas Charles L. , Bur Anthony J. 
Published: April 2004

AbstractWe have constructed an optical fiber sensor for monitoring injection molding and we have developed a model to describe sensor behavior. The sensor consists of a sapphire window at the end of a sleeved ejector pin into which an optical fiber is inserted. The optical view with this sensor is through the thickness of the molded product. The measured optical signal was light that transmitted through the resin, reflected off the back wall of the mold, and retraced its path through the resin to the optical sensor, i.e., light transmitted through twice the thickness of the resin. While monitoring polypropylene during the packing and cooling phase of the molding cycle, we observed a decrease in light intensity due to scattering of light by the growing microcrystals. A characteristic minimum in the transmitted light intensity versus time curve is attributed to scattering by growing crystalling spherulites at the core of the molded product. Cavity pressure was also measured and was found to be an essential parameter in the process model. The model illustrates how temperature, pressure, and crystallinity affect the detected light intensity and clarifies the roles that temperature and pressure play in the crystallization process.
Thermomechanical properties of radiation‐modified blends of polyethylene with liquid crystalline copolyester
Authors: Kalkis Valdis , Maksimov Robert D. , Zicans Janis 
Published: April 2004

AbstractThe results of investigation of gamma irradiated blends of high‐density polyethylene (PE) with thermotropic polymer liquid crystal (PLC) are presented. The PLC used was a copolyester of 40% poly(ethylene terephthalate) with 60% p‐(hydroxy‐benzoic acid). The PLC content in the blends was 0, 5, and 10 wt%. The constituents were blended with the use of a single screw extruder. The specimens were prepared by compression molding. The irradiation of the samples was performed by a Co60 γ‐radiation source in inert atmosphere (argon) up to absorbed relatively low doses (up to 200 kGy; 1 Mrad = 10 kGy). The morphological, thermal, and mechanical properties were investigated for irradiated and unirradiated samples. The influence of gamma irradiation and addition of PLC on the temperature dependence of the elastic modulus as well as the effect of a “form memory” of the materials examined are discussed. It was found that an addition of the PLC affects substantially the stress‐strain relationship in tension at temperatures above the melting point of PE for the irradiated samples. The features of thermomechanical behavior of the PE + PLC blends, previously irradiated and oriented, at isometrical heating and cooling were also established. The results obtained testify that the addition of PLC to PE makes it possible to improve considerably the thermosetting properties of the heat‐shrinkable polymeric products.
Stress oscillation in amorphous copolyesters due to tensile impact
Authors: Karger‐Kocsis J. , Czigány T. , Moskala E. J. 
Published: April 2004

AbstractSpecimens from amorphous copolyester (aCOP) sheets of different composition and molecular mass characteristics were subjected to instrumented tensile impact loading in the speed range of 2 – 3.7 m/s at ambient temperature. Stress oscillation was observed in the necking phase, especially for the aCOP with smaller entanglement density. It was found that the appearance of stress oscillation is limited to a given frequency or strain rate range (estimated by the ratio of the incident speed and clamped specimen length). Necking occurred by cold drawing which was evidenced by the shape recovery of the broken specimens when heated above the glass transition temperature (Tg ≈ 90°C). According to polarized light microscopy and differential scanning calorimetry (DSC), the stress oscillation was generated by diffuse shear banding without crystallization. This is the first report according to the authors' knowledge on the stress oscillation phenomenon in amorphous polymers in which crystallization was not involved.
Composites of poly(vinyl acetate) filled with calcium carbonate: Microscopy, diffractometry and thermophysical properties
Authors: Kovačević Vera , Lučić Sanja , Hace Draco , Packham David , Šmit Ivan 
Published: April 2004

AbstractCalcium carbonate (CaCO3) is used as filler in poly(vinyl acetate)(PVAc) composites to enhance the mechanical properties. The filler is often commercially surface treated with stearic acid to optimize the interfacial bonding and wetting. The effects of the interface on properties were studied using scanning electron microscopy (SEM) of films with initial and deformed morphologies. Plasticizing additives cause a significant change in the appearance of the films and a reduction in the glass transition temperature of the matrix from 40°C to ≈ 18°C, which was not altered by further addition of the filler. A PVAc composite fracture surface shows the particles adhering well to the matrix, suggesting good adhesion and reinforcement. The SEM study is complemented by WAXD, SEM/X‐SEM, XPS, and thermal analysis.