bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis of poly(oxyethylene‐styrene‐oxyethylene) triblock copolymers and their phase behavior
Authors: Xie Hongquan , Zhou Peiguang 
Published: December 2004

AbstractInteresting phenomena were observed in the polymerization of styrene and ethylene oxide into PEO‐PSt‐PEO triblock copolymers using potassium naphthalene as initiator and tolusene as a solvent. The relationship between the phenomena and molecular weight of the blocks was studied. The purified and characterized triblock copolymer showed mesomorphic behavior in toluene solution which depolarized polarized light increasingly as the concentration was increased. The structure of the triblock copolymer was also studied by small‐angle laser light scattering and by electron microscopy.
The unique properties of silicone and fluorosilicone elastomers
Authors: Cornelius D. J. , Monroe C. M. 
Published: December 2004

AbstractIn this paper a brief description of the synthesis of silicone polymers and their compounding is given, and the wide range of properties available in Silastic®Registered trademark of Dow Corning Corporation.
silicone rubber is discussed. Some of the key properties are related to several applications. These include mechanical properties, chemical and environmental resistance, thermal stability; electrical properties, flame resistance, and surface characteristics. Silicone rubber parts are currently used in the automotive, electronic, dairy, medical, construction, and aerospace industries. Among the applications discussed are axle seals, hose, milk inflations, wire and cable insulation, and elastomeric keyboard springs. In addition, improved silicone rubber materials are being developed for new applications.
Permeability barriers by controlled morphology of polymer blends
Authors: Subramanian P. M. 
Published: December 2004

AbstractMelt fabricated plastic articles with improved solvent and vapor barrier properties are of great need in the packaging industry. Various techniques, such as coextrusion, surface treatments, and coatings, are being employed currently towards this objective. Present work has identified a unique polymer blend approach to impart solvent and gas barrier properties to a polyolefin material. This involves incorporation of small amounts of a modified nylon barrier material, and processing under controlled conditions, in single step blowmolding or other extrusion processes. The unusual barrier effects obtained at small concentrations of the barrier material are obtained by the controlled morphology of the dispersed phase and optimum formulation of the ingredients.
Impact energy absorption of unidirectional glass fiber‐epoxy composites
Authors: Golovoy A. , Van Oene H. 
Published: December 2004

AbstractThe influence of resin and fiber properties on the impact behavior of composites can be assessed in a three‐point drop‐weight impact test by varying the length‐to‐thickness ratio of the specimen. The fracture initiation energy per unit deformed volume,wi, can be described by the expression:where τ11is the tensile stress, τ12is shear stress;E11is tensile modulus; andG12is shear modulus. A unidirectional glass fiberepoxy composite was tested at impact velocities of 2.2 m/s (5 mph) and 4.5 m/s (10 mph). The energy to initiate fracture,wi, was in the range of 2 to 3.5 MJ/m3, apparently independent of impact velocity. The total energy absorbed by the impacted composite was also found to be independent of impact rate but very sensitive to the length to thickness ratio: about 13 and 3.5 MJ/m3 at the corresponding ratios of 4.6 and 23. It was generally observed that high fracture energy is associated with extensive specimen delamination, i.e. failure in shear.
Studies on the melt flow behavior of thermoplastic elastomers from polypropylene—Natural rubber blends
Authors: Kuriakose Baby , De S. K. 
Published: December 2004

AbstractThe melt flow behavior of thermoplastic polypropylenenatural rubber blends has been evaluated with specific reference to the effects of blend ratio, extent of dynamic crosslinking of the rubber phase and temperature, on viscosity, flow behavior index, and deformation of the extrudate. The proportion of rubber in the blend and the extent of dynamic crosslinking of the rubber phase were found to have profound influence on the viscosity of the blends at lower shear stresses. But at higher shear stresses, the effect of blend ratio on viscosity was comparatively less for the uncrosslinked blends than that for the crosslinked blends. At lower shear stress, the viscosity of the blend increased with increase in degree of crosslinking but at higher shear stress, the effect of crosslinking on viscosity was found to vary depending on the ratio of the plastic and rubber components in the blend. The deformation of the extrudates was also very much dependent on both blend ratio and degree of crosslinking.
An engineering study of the film embossing process
Authors: Kamal M. R. , Haber A. , Ryan M. E. 
Published: December 2004

AbstractA mathematical model of the dynamics and heat transfer of the film embossing process has been developed. The thermal analysis around the preheat roll is determined from an unsteady, two‐dimensional heat conduction equation along with appropriate boundary conditions by neglecting the curvature of the preheat roll and choosing a Lagrangian reference frame. The heat transfer occurring between the preheat roll and the embossing rolls is based on a one‐dimensional analysis, including both convective and radiative effects. The deformation occurring in the nip region is analyzed for two different situations. For the case where the surface features are small in comparison with the film thickness, a modified one‐dimennsional calendering analysis is given, accounting for the irregular geometry of the embossing roll surface. For the case where the polymer does not make complete contact with the surface of the engraved channel, the local deformation is determined by means of a simple one‐dimensional cavity filling model. The required pressure distribution is determined by means of a simple one‐dimensional cavity filling model, The required pressure distribution is determined by means of a conventional calendering analysis. The analysis for the case of a Newtonian and power‐law model is presented in detail. The model yields qualitatively correct results and is computationally simple.
Evaluation of simple dynamic models and controllers for hydraulic and nozzle pressure in injection molding
Authors: Fara Dib Abu , Kamal M. R. , Patterson W. I. 
Published: December 2004

AbstractSimple pseudo‐steady state relations between the hydraulic and nozzle pressures of an injection molding machine were presented and verified experimentally. A simulation study was performed to evaluate the performance of simple controllers using dynamic models developed for the hydraulic and nozzle pressures. The controllers chosen were the discrete proportional, proportional‐integral (PI), and proportional‐integral‐derivative (PID) types, tuned according to the ITAE criterion. The control of hydraulic pressure simulation showed that the PI controller had the best overall performance, whereas the result of nozzle pressure control loop simulation showed that the PID controller performance was better than that of the PI controller. All the controllers, in both loops, gave responses that were about an order of magnitude more rapid than the open loop response.
Experimental study and analysis of a slit die viscometer
Authors: Rauwendaal Chris , Fernandez Franco 
Published: December 2004

AbstractA slit die viscometer (SDV) was built and evaluated extensively. A major advantage of the SDV is the ability to measure in‐line rheological data in a continuous fashion, using a setup that most closely approximates the conditions encountered in a real extrusion process. Comparisons will be presented of viscosity data of the SDV to data from a capillary rheometer (CR) and a Rheometrics Mechanical Spectrometer (RMS). Viscosity values as measured on the SDV tend to be lower than those measured on the CR and RMS. Possible reasons for this disagreement will be discussed. The effect of temperature on viscosity, the effect of pressure on viscosity, and the effect of compressibility will be analyzed in detail. It will be shown that these effects can be substantial, particularly with certain types of polymers. Finally, the feasibility of using the slit die viscometer to determine first normal stress differences will be explored.
Pressure build‐up during the packing stage of injection molding
Authors: Chung Tai‐Shung 
Published: December 2004

AbstractA thorough study of an isothermal fluid motion within the mold cavity during the packing stage is presented. The fluid is considered Newtonian, and its compressible behavior is assumed to obey the Spencer‐Gilmore equation of state. Mathematical results indicate that the pressure built up during the packing stage is strongly dependent on the melt viscosity and the boundary of the cavity. The effects of pressure gradient and distribution, during this stage, on the shrinkage of the final products are also discussed.
Viscosity of copolymers containing carbon black
Authors: Lakdawala K. , Salovey R. 
Published: December 2004

AbstractThe flow behavior of random copolymers of styrene and butyl methacrylate containing specific carbon blacks varying in surface area were studied at various temperatures and shear rates. Master curves of reduced viscosity as a function of shear rate were prepared for the pure copolymers at 150°C. The superposition required vertical and horizontal shifts, proportional to (aT)−1 and (aT).53, respectively, where aT is the shift factor. With the incorporation of carbon black, the viscous response is non‐Newtonian exhibiting a yield stress at increasing filler concentration and surface area. Master curves of viscosity against shear rate were generated at fixed filler loadings and surface areas by using a single horizontal shift factor.
The temperature‐dependence of some mechanical properties of a cured epoxy resin system
Authors: Gupta V. B. , Drzal L. T. , Lee C. Y.‐C. , Rich M. J. 
Published: December 2004

AbstractThe tensile mechanical properties and fracture toughness of a Bisphenol‐A type difunctional epoxy resin, cured with different amounts of metaphenylene diamine, using two cure cycles, were determined over a range of temperature. The tensile modulus in the glassy state was seen to be predominantly related to intermolecular packing, while in the rubbery state crosslink density was the important factor. Yielding appeared to be due to an increase in free volume as a result of dilatation during the tensile test and was related to a critical shear stress. The large strain properties like tensile strength, elongation‐to‐break, and toughness showed a more complex dependence on chemical structure, molecular architecture, intermolecular packing, and crosslink density. The roles played by the relaxation processes in determining mechanical properties are highlighted.
Impact strength and melt viscosity of bisphenol‐a polycarbonate and styrene‐maleic‐anhydride copolymer blends
Authors: Hansen Marion Glenn , Bland David G. 
Published: December 2004

AbstractMixtures of 90, 80, and 70 percent by weight bisphenol‐A‐polycarbonate (PC) and 10, 20, and 30 percent by weight styrene maleic anhydride (SMA) copolymer were melt‐blended in a single screw extruder. Differential scanning calorimetry (DCS) and scanning electron microscopy (SEM) were used to determine the miscibility of the blends. The viscosity, as a function of shear rate and temperature, was measured by an Instron capillary viscometer. The notched impact strength as a function of temperature was measured by an Izod impact tester.The results of DSC showed two glass transition temperatures which merged slightly towards each other, indicating marginal miscibility of these blends. There was a decrease in viscosity as the fraction of SMA copolymer was increased. The most significant decrease occurred with the initial addition of SMA copolymer. The viscosity also decreased with increases in temperature. The impact strength of the blends was also dependent on SMA copolymer content. The blends showed six to ten times lower impact strengths at room temperature than the 100 percent polycarbonate. SEM analysis helped to determine the reason why the impact strength was lower for the blends. High magnification showed the presence of SMA copolymer inclusions dispersed throughout the PC matrix. These inclusions, which increased in size as SMA copolymer content was increased, acted as defects in the system.
Instrumented impact testing of glass reinforced polypropylene
Authors: Golovoy A. 
Published: December 2004

AbstractThe impact response of a glass fiber reinforced polypropylene was studied in a 3‐point drop‐weight impact test between −15 and 85°C and at a constant impact velocity of 2.2 m/s (5 mph). The response is a combination of tension and shear and can be expressed in terms of an apparent modulus,EA: 1.WhereE11is the tensile modulus,G12: shear modulus,d: specimen thickness, andl: specimen length.For a 40 weight‐percent glass reinforced polypropylene,E11was found to have a room temperature value of 5.8 GPa, and shear modulus of 0.43 GPa. Both decreased with temperature increase, with the shear modulus showing greater sensitivity to a temperature change. The fracture initiation and propagation energies were relatively independent of temperature. The fracture initiation energy per unit deformed volume was of the order of 1 MJ/m3. The total fracture energy was found to be sensitive tol/d: about 7 MJ/m3atl/dof 5.3 and about 1.7 MJ/ m3atl/dof 16.
Dynamic‐mechanical and transient testing of practical plastic specimens using a new servo‐hydraulic testing system
Authors: Yee A. F. 
Published: December 2004

AbstractA servo‐hydraulic testing system which can simultaneously produce high loads and rapid response is described. This system allows the testing of relatively large plastic specimens, which makes it possible to perform dynamic‐mechanical and transient experiments on high modulus materials, specimens routinely molded for tensile testing, and specimens removed from actual processed articles. Such large specimens also permit the use of extensometers directly attached on the gage section, providing important data for the accurate calculations of material properties. Dynamic‐mechanical data on poly(methyl methacrylate), glass‐filled nylon, and talc filled polypropylene specimens removed from an injection‐molded dishwasher tub were obtained to demonstrate the capability of the system. Stress relaxation experiments in the nonlinear range were performed on polycarbonate to illustrate the transient testing capability of the system.
Phase behavior studies of the system polystyrene‐polybutadiene‐chloroform. I. Application of the flory‐huggins theory
Authors: Robledo‐Muniz J. G. , Tseng H. S. , Lloyd Douglas R. , Ward Thomas C. 
Published: December 2004

AbstractThe equilibrium phase behavior of the partially miscible system polystyrene‐polybutadiene‐chloroform was studied at 25°C and 1 atm pressure by using gel permeation chromatography to analyze the conjugate phases. Three narrow molecular weight distribution samples of each polymer were used to provide nine examples of the system for study. The Flory‐Huggins theory was used to determine the polymer‐polymer interaction parameter χ23, When literature values of the two polymer‐solvent interaction parameters χ12 and χ13 were used, the χ23 values generally were found to be negative and to show no distinct concentration dependence. No significant improvement was found when the literature value of only the polybutadiene‐chloroform interaction parameter was used to simultaneously generate values of χ23 and χ12. Values of χ23 at the critical point, χ23,cr, were found to increase with increasing polymer concentration.
A study on polymer blending microrheology: Part 1
Authors: Elmendorp J. J. , Maalcke R. J. 
Published: December 2004

AbstractIn order to achieve a better understanding of polymer blending processes some experimental work has been carried out on the deformation and break‐up behavior of liquid droplets in simple shearing matrices. For Newtonian systems good agreement was obtained with existing theories. For non‐Newtonian systems trends were established regarding the influence of fluid elasticity on droplet deformation and break‐up.
Studies of poly(2,6‐dimethyl‐1,4‐phenylene oxide) blends: 2. Poly(4‐methylstyrene)
Authors: Fried J. R. , Lorenz T. , Ramdas A. 
Published: December 2004

AbstractBlends of poly(2,6‐dimethyl‐1,4‐phenylene oxide) (PMMPO) and poly(4‐methylstyrene) (P4MS) were found to be compatible from a variety of experimental methods including calorimetric, density, and mechanical property measurements. Blend property behavior was similar to that widely reported for PMMPO/polystyrene (PS) blends. For each blend composition studied, a single glass transition temperature (Tg) was detected by differential scanning calorimetry. The compositional dependence of blend Tg was equally well represented by the empirical inverse rule of mixtures or by the Couchman thermodynamic expression. Density measurements of molded films suggested a mild excess volume of mixing that was slightly smaller than that observed for blends of PMMPO and PS. As in the case for PMMPO/PS, densification in the solid state may be associated with the observed mechanical property behavior of the PMMPO/P4MS blends. Initial modulus at each blend composition was larger than would be predicted by a simple weighted average of component polymer values. Tensile deformation changed from a ductile to a brittle mode of failure with increasing P4MS composition. The yield stress for ductile compositions and ultimate stress of brittle samples were both higher than found for the corresponding unblended polymers and higher than would be predicted from a simple additive relationship of weighted component properties. Blend impact strength determined by small strain rate tensile tests rapidly decreased to low levels with increasing P4MS composition. This drop in impact strength became more composition sensitive at higher loading rates during multiaxial deformation in an instrumented dart impact tester.
Equilibrium phase compositions of heterogeneous copolymers
Authors: Bauer Barry J. 
Published: December 2004

AbstractThe products of random copolymerizations are heterogeneous in chemical composition, having a distribution of the fraction of each monomer in the copolymer. Polymer molecules with the same composition and molecular weight can be treated as separate components in a polymer blend. The spinodal limit is a simple function of chemical heterogeneity. The equilibrium number of phases, phase volumes, and average composition can be calculated from the condition that the chemical potential of a polymer species is equal in every phase. Phase diagrams are calculated for various hypothetical chemical distributions as well as a distribution characteristic of a random acrylonitrilebutadiene copolymerization to high conversion.
Theory of phase equilibria in block copolymer‐homopolymer mixtures
Authors: Whitmore Mark Douglas , Noolandi Jaan 
Published: December 2004

AbstractA brief introduction to the theory of block copolymer/homopolymer mixtures is presented. All important effects, such as stretching of the polymer chains, changes in the conformational entropy at an interface, enthalpic and configurational effects, as well as connectedness of the blocks of the copolymer are included in the model.
Dynamic mechanical analysis of rubber toughened epoxy resins
Authors: Sanjana Z. N. , Kupchella L. 
Published: December 2004

AbstractDynamic mechanical analysis (DMA) was used to characterize cured epoxy resin formulations from −150°C to temperatures above their α transitions. The resins were aromatic amine and aliphatic amine cured and were modified with carboxylterminated acrylonitrile‐butadiene (CTBN) rubbers to improve their toughness, A DuPont 981 dynamic mechanical analyzer was used to measure the modulus and mechanical loss factor (tan δ) of the samples. Changes in the α and β transitions in the scan of tan δ as a function of temperature were related to changes in the formulation. Relations were also sought between changes in the DMA data and fracture and impact toughness of the cured formulations obtained using an instrumented impact test. Impact tests were performed at −196°C and at room temperature. Results indicate that fracture toughness and the dynamic mechanical properties are affected by the amount of rubber, the compatibility of the rubber and epoxy, and changes in the curing agent stoichiometry.
Tube flow of a particulate‐filled thermosetting polymer
Authors: Riccardi C. C. , Vazquez A. 
Published: December 2004

AbstractThe conservation equations of momentum, energy, and mass are numerically solved for the flow of filled thermosets reacting In a tube. The flow is assumed to be laminar and adiabatic with a constant volumetric flow rate. The critical radii are parameters that define the processability limits. The lower one is the value of the radius where an undesirable advance in the reaction extent takes place at the wall or where viscous heating leads to degradation. The upper critical radius is the radius where wall velocity is low and gelation takes place. The effects of filler volumetric fraction, wall slip velocity, and different inlet conditions are taken into account. Increasing wall slip velocity or filler fraction and decreasing inlet temperature or tube length amplify the processability zone.
Melt homogeneity in injection molding: Application of a ring‐bar device
Authors: Peischl G. C. , Bruker I. 
Published: December 2004

AbstractA thermocouple ring‐bar device located between the nozzle and screw‐tip was used to study the thermal homogeneity of a shot formed during injection molding. Axial and radial melt temperature profiles thus observed under various processing conditions illustrated the importance of screw channel volume‐to‐short‐size ratio on melt homogeneity, Several methods of improving melt quality, as measured by this device, are demonstrated.
Melting mechanism in single screw extrusion
Authors: Bruker Izi , Balch Gary S. 
Published: December 2004

AbstractFlow visualization experiments of polycarbonate and polystyrene resin extrusion were performed to observe the melting mechanism and the flow kinematics around the solid‐bed in the melting zone of a single screw extruder. The axial solids content and pressure profile calculations of the Tadmor melting model were modified as a result of variable solid‐bed velocity and solid‐bed temperature observations.
Simultaneous dielectric and dynamic mechanical analysis of thermosetting polymers
Authors: Gotro Jeffrey , Yandrasits Michael 
Published: December 2004

AbstractThis work presents a new method to measure simultaneously the dielectric loss factor and viscosity of thermosetting polymers during various cure cycles. A microdielectric sensor was mounted in the bottom plate of a parallel plate rheometer. Three types of high performance laminating resins were investigated. During non‐isothermal curing, dipole peaks were found to correspond to softening/devitrification, the maximum in the loss factor followed the same heating rate dependence as the minimum in the viscosity, and dipole peaks were observed to correlate with vitrification when the cure temperature was below the ultimate glass transition temperature of the resin.