bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mechanical and viscoelastic properties of semi‐interpenetrating polymer networks of poly(vinyl chloride)/thermosetting resin blends
Authors: Pittman Charles U. , Xu Xiaoming , Wang Lichang , Toghiani Hossein 
Published: April 2004

AbstractSemi‐interpenetrating polymer networks (SIPNs) of PVC/thermoset were prepared by premixing porous, 150 μm diameter particles of PVC and a small quantity (from 5 to 15% by weight) of a single thermosetting liquid preresin from one of five types (e.g. methylene bis‐phenyl diisocyanate (MDI), oligomeric MDI isocyanates (PAPI), toluene diisocyanate (TDI) prepolymer, epoxy, and vinyl ester resins, respectively). Two roll milling of these mixtures was followed by hot‐press curing. Mechanical testing indicated that most of these blends exhibited increased tensile, impact, and flexural strengths. The strength increments were greater when going from 0 to 5% thermoset content than when going from 5 to 10% or 10 to 15% thermoset. In many cases, increasing thermoset content from 10 to 15% gave slightly decreased or unchanged tensile, impact, and flexural strengths. This behavior is in accord with a “thermoset dilution effect” in PVC. Most of these SIPN blends exhibited a tan δ peak temperature lower than that for pure PVC in the glass transition region. The tan δ peak temperatures were progressively lowered as the amounts of thermoset increased. Also, a single distinct peak existed in the E″ curves for most of the blends. Only the PVC/epoxy (90/10) blend showed two peak maxima in E″ vs. temperature curves. All blends exhibited peak E″ values at a lower temperature than those of PVC which had been exposed to the same processing temperatures. These observations seem to rule out the presence of large domains of PVC, which are phase‐separated from PVC/thermoset SIPN, and pure thermoset domains. A substantial amount of the added thermoset appears to exist in SIPN type phases in these five blend types.
Cure kinetics and properties of epoxy/dicyanate blends
Authors: Kim Dae Su , Shin Ju Ho 
Published: April 2004

AbstractThe cure behavior and properties of epoxy/dicyanate blends containing a stoichiometric amount of an amine curing agent for epoxilde groups were investigated as a function of blend composition. Differential scanning calorimetry (DSC) was used to investigate the dynamic and isothermal cure behavior of the blends. The cure rate of the blend increased with increasing dicyanate content. A second order autocatalytic reaction mechanism described the cure kinetics of the blends. The kinetic parameters were determined by fitting the dynamic DSC data to the model kinetic equation. The k10 and E1 values were mainly affected by the change of dicyanate content. The glass transition temperature of the blend decreased with increasing dicyanate content. The thermal decomposition characteristics of the blends were investigated by thermogravimetric analysis (TGA). Dynamic mechanical analysis (DMA) and thermal mechanical analysis (TMA) were used to investigate the mechanical properties of the blends. With increasing dicyanate content, the cure rate increased but the thermal and mechanical properties of the cured blends were not improved.
Temperature dependence of work of fracture parameters in polybutylene terephthalate (PBT)
Authors: Hashemi S. 
Published: April 2004

AbstractEssential work of Fracture (EWF) analysis was used to study the effect of temperature on fracture toughness of PBT film. Using Double Edge Notched Tension (DENT) specimens, it was found that between +25°C and +80°C, the specific essential work of fracture,we, of PBT film is independent of temperature, having an average value of 33.40 kJ/m2. Thewevalue was reduced to 27.51 kJ/m2as temperature was raised to 100°C. It is demonstrated that both specific essential (we) and non‐essential work of fracture (βwp) terms can be partitioned into two components, one linked to yielding (we,yand βywp,y) and the other to necking/tearing (we,n tand βntwp,nt), of the ligament region. The essential terms,we,yandwe,nt, were lowest at 100°C, having values of 9.14 kJ/m2and 18.57 kJ/m2, respectively, compared to 14.83 kJ/m2and 19.17 kJ/m2obtained at 25°C. As for non‐essential work tems, it was found that βywp,ydecreased with increasing temperature, whereas change in βntwp,ntand βwpvalues was dependent on the temperature range being considered.
Efficient mixing of polymer blends of extreme viscosity ratio: Elimination of phase inversion via solid‐state shear pulverization
Authors: Furgiuele Naomi , Lebovitz Andrew H. , Khait Klementina , Torkelson John M. 
Published: April 2004

AbstractA novel, continuous process, solid‐state shear pulverization (S3P), efficiently mixes blends with different component viscosities. Melt mixing immiscible polymers or like polymers of different molecular weight often requires long processing times. With a batch, intensive melt mixer, a polyethylene (PE)/polystyrene (PS) blend with a viscosity ratio (low to high) of 0.019 required up to 35 min to undergo phase inversion. Phase inversion is associated with a morphological change in which the majority component, the high‐viscosity material in these blends, transforms from the dispersed to the matrix phase, and may be quantified by a change from low to high mixing torque. In contrast, such blends subjected to short‐residence‐time (∼3 min) S3P yielded a morphology with a PS matrix and a PE dispersed phase with phase diameters ≤ 1 μm. Thus, S3P directly produces matrix and dispersed phases like those obtained after phase inversion during a melt‐mixing process. This assertion is supported by the similarity in the near‐plateaus in torque obtained in the melt mixer at short times with the pulverized blend and at long times with the non‐pulverized blend. The utility of S3P to overcome problems associated with melt mixing like polymers of extreme viscosity ratio is also shown.
Rheological behavior of a polymerically stabilized latex for use in water‐borne coatings
Authors: Shay Jennifer S. , English Robert J. , Khan Saad A. 
Published: April 2004

AbstractA unique urethane linkage that permits chemical grafting of poly(ethylene oxide) (PEO) linear chains to the surfaces of polystyrene (PS) latex particles has been developed. Chemically grafting the functionalized hydrophilic PEO macromers to the PS particle surface allows the latex to be polymerically stabilized in a water‐based medium. Advantages of the urethane linkage include the high yield of the macromer synthesis and the hydrolytic stability of the final latex. Rheological experiments are used to examine both processing behavior and interparticle interactions for latex systems with different amounts of grafted PEO. Dynamic rheological experiments reveal that, at high macromer concentrations, the grafted PEO layer is effective in shielding the attractive interactions of the core PS particles that lead to flocculation. However, at low macromer concentrations, strong interactions are seen even at low particle weight fractions, indicating the presence of a flocculated system. Steady shear rheological evaluations show that the latex systems possessed suitable flow behavior for coating applications, even at relatively high particle weight fractions. Experimental steady shear data is utilized in conjunction with the Krieger‐Dougherty equation to determine the size of the PEO stabilizing layer. The stabilizing layer thickness decreases as particle concentration increases, indicating a compressible system. Finally, the relationship between the strength of interparticle interactions and PEO graft density is gauged from the dependence of the power‐law exponent of the elastic modulus on particle concentration.
Modeling of molecular weights in industrial autoclave reactors for high pressure polymerization of ethylene and ethylene‐vinyl acetate
Authors: Sarmoria C. , Brandolin A. , López‐Rodríguez A. , Whiteley K. S. , Fernández B. Del Amo 
Published: April 2004

AbstractWe have incorporated mass balances of monomer, radical and polymer species to a previously developed mixing model for high pressure autoclave polymerization reactors. The customary quasi steady state approximation is not used, and the method of moments is used to simplify the mass balance calculations. The resulting moment model is able to calculate conversions, average molecular weights, long chain branching and melt flow indexes at any point in the reactor. It may also calculate concentration and temperature profiles along the reactor. Results for two base cases are presented in detail. Model predictions were compared with experimental data obtained at the industrial reactor; excellent agreement was obtained. The moment balance equations are presented in a modular way so that they may be easily adapted to be used with any other mixing model for this type of reactor.
Thermal cycling of plastics—relaxation and set in polycarbonate and polypropylene
Authors: Fesko Donald G. 
Published: April 2004

AbstractThe residual stress state or the amount of permanent set as a result of thermal cycling a plastic specimen white it is restrained can be estimated by a simple model using the thermal expansion coefficient, modulus vs. temperature data, stress relaxation data and knowing the time spent at elevated temperature. This offers the opportunity to model the end result of thermal cycling of plastic components by finite element analysis (FEA) without resorting to a viscoelastic FEA. The method combines the developed thermal strain with the relaxation taking place at the elevated temperature for the elapsed time and assumes the set is frozen in on cooling. Experimental data for polycarbonate and polypropylene show the method to be a good approximation. Data also show that it works for multiple cycles by simply treating the accumulated time at elevated temperature.
Polystyrene microcellular plastic generation by quick‐heating process at high temperature
Authors: Sumarno  , Sunada Tomoko , Sato Yoshiyuki , Takishima Shigeki , Masuoka Hirokatsu 
Published: April 2004

AbstractGeneration of microcellular plastic in the polystyrene‐nitrogen system was studied in a batch process. In this study, a quick‐heating method was applied to study the effects of saturation temperature, decompression rate and heating time on the microcellular structure for sheet samples with a thickness of 1.3 mm. The saturation pressure in each process was kept constant at 25 MPa. At saturation temperatures above 393 K, we found that, although the solubility of nitrogen increased with increasing saturation temperature, cell density decreased, and the average cell diameter and volume expansion ratio increased. The samples that were saturated at 433 K shattered after microcellular processing. The change in decompression rate affected the supersaturation degree of the dissolved gas in the polymer, and affected the cell structure. Variation of heating time for difference saturation/heating temperature could be used to obtain the optimum relation between cell density, average cell diameter, and volume expansion ratio.
Copolymerization of carbon dioxide and propylene oxide using various zinc glutarate derivatives as catalysts
Authors: Ree M. , Bae J. Y. , Jung J. H. , Shin T. J. , Hwang Y.‐T. , Chang T. 
Published: April 2004

AbstractVarious zinc dicarboxylate catalysts were synthesized by the reaction of zinc oxide with eleven different glutaric acid derivatives, and their coordination characteristics were investigated by infrared spectroscopy. The electronic nature and steric hinderance of substituents influenced the coordination of the carboxylate and the zinc metal ion. The coordination characteristics were classified into three categories: (i) compounds exhibiting bridging bidentate coordinating bonding modes, such as syn‐anti and syn‐syn bridging; (ii) compounds with only unidentate coordination; and (iii) compounds with mixed coordinations of unidentate and bridging bidentate. All the zinc carboxylate catalysts produced poly(propylene carbonate)s (PPCs) by the copolymerization of carbon dioxide and propylene oxide. The first category of catalysts produced relatively higher yields than the other categories. Zinc glutarate without any substituent, which is a catalyst in the first category, produced PPC with the highest yield and the highest molecular weight. The catalytic activity of zinc glutarate was suppressed by incorporation of substituents. The suppression of the catalytic activity might be due to the variation in the Lewis acidity of the zinc site as well as changes in the morphological structure caused by the substituents. Methylaluminoxane was also evaluated as a catalyst for the copolymerization, but it produced copolymers containing a large amount of ether linkages.
Deformational behavior of polyolefins at high temperature and strain rate: Experimental analysis and constitutive laws
Authors: Briatico‐Vangosa Francesco , Rink Marta , D'Oria Francesco , Verzelli Alberto 
Published: April 2004

AbstractLarge deformation behavior of two polyolefins has been investigated under high temperatures and high strain rate conditions. During uniaxial tensile tests at constant true strain rate, volume, stress, and deformation ratio were measured. At the temperatures considered, the mechanical behavior tends to be elastic (rate‐independent) as strain rate increases. Thus elastic models can be used to describe the deformational behavior of these resins under such conditions. Models proposed by Ogden, by Coleman as modified by Radi, and by Sweeney‐Ward have been considered to fit experimental data and their adequacy has been discussed. Sweeney‐Ward's model has been found to provide the best fit of the examined polymer's behavior at high temperatures and high strain rates.
Elongational behavior of polyethylene melts—effect of deformation
Authors: Micic P. , Bhattacharya S. N. 
Published: April 2004

AbstractTransient elongational viscosity of linear low density polyethylene (LLDPE) and two low density polyethylenes (LDPE1 and LDPE2) was measured at one temperature and different deformation rates in constant strain rate elongational rheometer. The elongational viscosity measurements revealed stronger strain hardening characteristics for LDPEs than that observed for LLDPE. The different response to stretching of these polymers is thought to relate to the presence of long chain branches in LDPEs, which affect the elongation viscosity profoundly. The onset of strain hardening for all long chain branched LDPEs as well as for linear LLDPE occurs at the same value of the critical strain, which is independent of temperature or deformation rate. An attempt has been made to explain this phenomenon in terms of the changes that occur in the macromolecular network upon stretching.
Draft angle and surface roughness effects on stereolithography molds
Authors: Cedorge Thomas , Colton Jonathan 
Published: April 2004

AbstractStereolithography (SL) is a rapid prototyping process, which allows one to build complex shapes quickly. Current research investigates the possibilities of using this process to make injection molds. This would allow designers to manufacture and test molds easily and rapidly. One of the main issues with this technique is the effects of its surface on the part. Molds built by SL have high roughness. This gives rise to a high friction force between the part and the mold, and increases the ejection force needed to eject the part from the mold. High ejection forces often lead to damage or breakage of the part and the mold. Research was undertaken on the effects of draft angle and roughness on ejection forces. It was found that increasing the draft angle does not necessary assist the ejection of the part. As the draft angle increases, the roughness and hence the friction force between the part and the mold also increase. There is a trade‐off between draft angle and roughness. A model based on Glanvill's equation was developed to predict ejection force and was consistent with experimental results.
Peroxide‐catalyzed swell grafting of maleic anhydride onto polypropylene
Authors: Ko Tze‐Man , Ning Ping 
Published: April 2004

AbstractA new grafting method was developed to incorporate maleic anhydride directly onto solid‐state polypropylene powders. Maleic anhydride grafts altered the nonpolar characteristics of polypropylene so that much better mixing was achieved in blends and composites of polypropylene with many other polymers and fillers. Maleic anhydride was grafted onto polypropylene by the peroxide‐catalyzed swell grafting method, with a maximum extent of grafting of 4.60%. Fourier transform infrared spectroscopy, differential scanning calorimetry, thermogravimetric analysis, scanning electron microscopy, tensile testing, and impact testing were used to characterize the isotactic polypropylene (iPP), maleic anhydride grafted polypropylene (MAH‐g‐iPP), and (isotactic polypropylene)/(calcium carbonate) composites (iPP/CaCO3). The crystallinity and heat of fusion of the MAH‐g‐iPP decreased as the extent of grafting increased. The mechanical properties of the CaCO3 filled polypropylene were improved by adding MAH‐g‐iPP as a compatibilizing agent. The dispersion of the fillers in the polymer matrix and the adhesion between the CaCO3 particles and the polymer matrix were improved by adding the compatibilizer.
Synthesis of poly(2,5‐di‐n‐butoxy‐p‐phenylene vinylene) and its application in light‐emitting diodes
Authors: Wang Guojie , Huang Jingsong , Li Min , Chen Xinfang , Liu Shiyong 
Published: April 2004

AbstractPoly(2,5‐di‐n‐butoxy‐p‐phenylene vinylene) (DBPPV) was synthesized in a mixed solvent of xylene and tertbutyl alcohol via a dehydrochlorination route, using potassium tert‐butoxide as the initiator. The polymer was soluble in organic solvents such as xylene, chloroform and THF. The polymer was characterized by elemental analysis, FTIR, 1H NMR and UV‐Visible spectroscopy. Single‐layer and a double‐layer light‐emitting diodes (LEDs) were fabricated using the polymer as the active layer. The peaks of the photoluminescence (pl) and electroluminescence (el) spectra of the LEDs were at 580 nm and 577 nm, respectively. The turn‐on voltage and the maximum luminescence of the single‐layer LED were 6.4V, and 100 cd/m2, while that of the double‐layer LED were 4.3V, and 630 cd/m2, respectively.
Mechanical and thermal anisotropy for uniaxially and biaxially drawn PET
Authors: Ellis John W. , Picot J. J. C. 
Published: April 2004

AbstractSheets of two molding grades of polyethylene terephthalate (PET) with weight average molecular weight of 57,000 and 52,000 were drawn uniaxially or biaxially to ratios of up to 3 in a compression mold at 200°C. Tensile modulus measurements were done for axial and transverse strain. Thermal conductivity measurements were done with a transient‐state surface probe for thermal conductivity in the normal‐to‐the surface direction (Kn), as well as the axial (Ka) and transverse (Kt) directions in the plane of the sheet. Values are presented as normalized by the tensile modulus (Mo) or the normal conductivity (Kno), respectively, of undrawn isotropic specimens. For the uniaxial experiments, both M/Mo and Ka/Kno were linearly related to draw ratio. A regression analysis on results for both grades of PET for Ka/Kno in terms of M/Mo gave Y = 0.804*X + 0.286; std. err. of Y est. equal to 0.17. Kn/Kno decreased slightly. This non‐intrusive conductivity measurement provides a convenient means for monitoring the development of increased modulus in hot‐forging processes. Results on biaxially oriented specimens showed lesser modulus increases with draw ratio, consistent with orientation distribution in a plane, rather than in a single direction. Thermal conductivity (Ka/Kno as well as Kt/Kno), however, increased to a greater degree than for the case of uniaxial draw for the higher molecular weight material, suggesting the possibility of tilting of crystalline aggregates in the deformation process.
Nondestructive testing of polyaramide cables by longitudinal wave propagation: Study of the dynamic modulus
Authors: Ferreira M. , Lam T. M. , Koncar V. , Delvael Y. 
Published: April 2004

AbstractIt has been observed that cables at different states of fatigue had their own speed of longitudinal propagation of acoustic waves (1). This speed can be measured with piezoelectric captors and is proportional to the square root of the sonic modulus. Our experiments, which have been carried out on Technora cables of diameter 2 mm, show that the modulus obtained from the wave speed has the same behavior in fatigue as the modulus obtained from tensile tests. Furthermore, our experiments also show that the residual strength in the cable is proportional to the modulus. A nondestructive control of cables can hence be made from these sonic modulus measurements.
Thermal, mechanical, and diffusional properties of nylon 6/ABS polymer blends: Compatibilizer effect
Authors: Jang Seung Phil , Kim Dukjoon 
Published: April 2004

AbstractThe thermal, mechanical, and water absorption properties of blends of nylon 6 (PA6) and acrylonitrile‐butadiene‐styrene copolymer (ABS) with and without the compatibilizer maleic anhydride (MAH) were studied. Polymers were melt‐blended using a twin screw extruder, and injection molded into sheets. Tensile and impact properties, hardness, heat deflection resistance, and dimensional stability were enhanced by the incorporation of MAH. Synergistic effects were observed for tensile elongation and flexural properties. The melting temperature and the thermal stability were not significantly affected by the incorporation of MAH. The mechanical property enhancement by the introduction of compatibilizer was explained by the formation of a micro‐domain structure in the blends. The equilibrium water uptake increased with increasing concentration of PA6, and the diffusion coefficient was determined from the water transport kinetics at different temperatures. Activation energy was extracted from the temperature dependence of the diffusion coefficient. No compatibilizer effect was observed in the swelling behavior.
Flow behavior of LCP melts and its influence on morphology and mechanical properties of injection molded parts
Authors: Nguyen T. N. , Geiger K. , Walther Th. 
Published: April 2004

AbstractThe flow behavior of two commercial liquid crystalline polymers (LCP), Vectra B 950 and Vectra L 950 (Ticona GmbH), was investigated using a capillary rheometer with a new double slit die. The influence of pre‐shearing of the melt on its viscosity and the apparent geometry dependence of its flow behavior were analyzed. The dependence of flowability on the part was determined with a modular spiral mold in which the thickness of the channel was varied. The influence of processing parameters and part geometry on the mechanical properties and morphology of molded parts was also studied.