bluuebunny/crossref_metadata_2025_split huggingface dataset:
Polystyrene‐polyethylene melt blends obtained through reactive mixing process
Authors: Baker W. E. , Saleem M. 
Published: December 2004

AbstractReactive polystyrene (OPS) and reactive polyethylene (CPE) with oxazoline and carboxylic acid functionality, respectively, were melt blended in a Rheomix mixer under a variety of conditions. The properties of these blends were examined and correlated with the compositions and mixing conditions such as shear rate, time, and temperature. An increase in torque was observed, which is believed related to chemical reaction between OPS and CPE. The difference between the maximum and minimum torque (Tmax‐Tmin), increases from 48 to a maximum of 510 m‐g for 10 and 40% CPE reacted blends, respectively, But on further increase in the CPE amount in the blend the torque increase drops reaching a final minimum value of 133 m‐g for a blend with 90% CPE. Differential Scanning Calorimetry (DSC) studies reveal a single first order transition, due to CPE, for each of these polymer blends. Furthermore, evidence of the glass transition temperature for OPS diminishes with increasing CPE content and mixing time. Scanning Electron Micrographs (SEM) show a fine dispersion in these reactive blends, with particle size much smaller than a micron. Blends with 50% or more CPE have no distinguishable features as such. Mechanical properties such as elongation at break of reacted blends are improved over the nonreactive polyethylene (PE) and polystyrene (PS) blends. An intermolecular reaction between the OPS and CPE results in a graft polymer, which imparts improvement in the overall properties of these reacted blends. The maximum grafting reaction corresponds to 40% CPE blend, which is being evaluated as a potential compatibilizer.
On the pressure of water of crystallization at filler inclusions
Authors: Ashbee K. H. G. 
Published: December 2004

AbstractOn water uptake, plaster of Paris sets to gypsum, and the volume expansion associated with this particular hydration reaction has been long exploited to make casts for statuary. Immobilization of molecules of liquid water into the crystal lattice of water of crystallization gives rise to a decrease of entropy, and this is manifested by the so‐called heat of hydration. When it occurs at a calcium sulfate inclusion inside a polymer, the plaster of Paris → gypsum reaction generates a pressure, and the dependence of the equilibrium value of this pressure on temperature is expressed by Clapeyron's equation. From published data for the volume expansion ΔV and entropy decrease ΔS, it is shown that

Using as a benchmark the fact that p is zero at 100°C, the temperature at which plaster of Paris, gypsum, and liquid solution can exist in thermodynamic equilibrium (1), we find that hydration at ambient temperatures of a typical calcium sulfate filler composition will, under conditions of thermodynamic equilibrium, generate sufficient pressure to cause internal cracking. Attention is drawn to the fact that creation of water of crystallization pressures of similar magnitude can be expected for any other filler that can exist in more than one state of hydration. As a corollary, the Clapeyron equation is used to make a similar analysis of the phenomenon of frost shattering in polymeric materials that contain free water.
Viscosity of homogeneous polymer blends: An altered free‐volume state model
Authors: Sood R. , Kulkarni M. G. , Dutta A. , Mashelkar R. A. 
Published: December 2004

AbstractAn altered free‐volume state (AFVS) model was developed for the zero‐shear viscosity of homogeneous polymer blends. The model involves a single adjustable parameter and is capable of predicting several complex features of the blend viscosity‐composition behavior. These include negative and positive deviations from additivity, maxima, minima, and sigma‐shaped curves. The validity of the model was tested by comparison of the model predictions with experimental data for several homogeneous blend systems. It is shown that the model is valid within a broad molecular weight range and is more accurate than some of the currently accepted models such as the kinetic network model. Besides, it appears that the AFVS model also may be applicable to blends of incompatible polymers under certain conditions.
Anomalous penetrant transport in glassy polymers VI. Effect of temperature on transport
Authors: Urdahl Kent G. , Peppas Nikolaos A. 
Published: December 2004

AbstractTransport of liquid cyclohexane through well characterised, initially glassy, crosslinked polystyrene slabs was Investigated at 20, 30, 40, and 50°C. The samples used were produced by bulk polymerization of styrene and divinyl benzene (DVB) at 90°C for 43 hr using benzoyl peroxide as an initiator. The samples tested had initial cross‐linking ratios, X, between 5 and 25 × 10−3 mol DVB/mol styrene. The initial thickness of the samples tested varied from 0.25 mm to 1.80 mm, and the aspect ratio (length to thickness ratio) was maintained above 10;1 in order to analyze the results by one‐dimensional transport equations. Cyclohexane uptake was followed as a function of time along with dimensional changes in the thickness and area of the samples. The results of penetrant uptake as a function of time were analyzed using a simplified exponential expression and employing all the data points from the beginning of the experiment until the time of observation of the maximum in uptake. Good correlations were established between the penetrant uptake and the transport temperature. These results were interpreted in terms of competitive relaxational and diffusional mechanisms.
Optimal anticipatory control of ram velocity in injection molding
Authors: Pandelidis I. O. , Agrawal A. R. 
Published: December 2004

AbstractThis paper discusses a computer control system for ram velocity of an injection molding machine using optimal state feedback based on the linear quadratic control theory. A new approach for the selection of appropriate weighting matrices is presented in this context. The simulation results reveal that the optimal controller has improved performance over the conventional PID controller presently used, having faster speed of response, significantly better tracking performance, and better noise filtering properties. The execution speed and the core storage requirements would allow implementation even on a small online computer.
Hydrolysis of polycarbonate/polybutylene terephthalate blend
Authors: Golovoy A. , Cheung M. F. , Van Oene H. 
Published: December 2004

AbstractThe hydrolysis of a polycarbonate/polybutylene terephthalate (PBT) blend (50/50) was investigated by immersing molded samples in water baths between 21 and 98°C. Samples were also placed in a 100°C air circulating oven (dry environment). Changes in impact properties, dynamic mechanical properties, molecular weight, and thermal properties were followed. In 80°C water bath the material was found to embrittle in five to six days, and in circulating air oven at 100°C in less than 90 days. A sharp decline in molecular weight and changes in thermal and mechanical properties were observed. The activation energy for the embrittlement process in water was found to be 22 kcal/ mole. This value is between the activation energy for the hydrolysis of PC and that of PBT.
Effect of crosslink density on molecular relaxations in diepoxide‐diamine network polymers. Part 2. The rubbery plateau region
Authors: Charlesworth John M. 
Published: December 2004

AbstractA comparison of the prediction of the theory of rubber elasticity with the experimentally observed variation of the shear storage modulus, G, as a function of crosslink concentration shows that deviations occur when the network strand concentration in diepoxide‐diamine polymers exceeds approximately 1.5 mole kg−1. The rapid rise in G above this level is accounted for in terms of the increasing importance of non‐Gaussian chain statistics and steric interactions. It is also established that the contribution from entanglements is significant and the behavior over the entire crosslink density range can be described by the following equation

where v and ϵTe are the concentrations of elastically active strands which orginate from fixed points and entanglements respectively, ψ is an empirical constant related to the importance of the non‐ideal behavior, and ϕ is the so‐called “front factor”. This latter constant is found to depend on the functionality of the network junctions, varying from 0.9, for a system with tetrafunctional junctions, to an average of 0.53 for those networks with trifunctional junctions.
Mold‐filling simulations for the injection molding of continuous fiber‐reinforced polymer
Authors: Chan A. W. , Hwang S.‐T. 
Published: December 2004

AbstractInjection molding can be used to fabricate fiber‐reinforced polymer composites by impregnating a continuous fabric mat preplaced in a mold cavity with a polymer resin. The mold‐filling time is dependent on the flow and heat transfer behavior in the mold. A model is proposed that considers the non‐Newtonian How through the porous fabric mat and the heat transfer between mold, fabric mat, and flowing fluid. The model was simulated for the mold filling of a carbon fiber mat with a pseudoplastic polymer solution. The results from the simulation provide Information for optimizing mold‐filling parameters through proper selection of inlet fluid pressure, heat source temperature, and type of polymer‐solvent system.
Cure analysis of printed wiring boards containing reactive adhesive layers
Authors: Fullerton Rhonda , Roylance David , Allred Ronald , Acton Adra 
Published: December 2004

AbstractThis paper presents a method for analyzing the cure of multilayer circuit boards containing chemically reactive adhesive interlayers. The cure kinetics of the adhesive are first quantified by differential scanning calorimetry, using the method of Freeman and Carroll to obtain the numerical kinetic parameters. These parameters are then used in a finite‐element model of the circuit board which solves the heat and species transfer equations simultaneously. It is then possible to predict the temperature and extent of reaction at any time and position within the laminate, enabling the curing program to be optimized.
A mathematical model for computer simulation of a direct continuous esterification process between terephthalic acid and ethylene glycol
Authors: Yamada T. , Imamura Y. 
Published: December 2004

AbstractTo study the effect of potassium titanium oxyoxalate on the esterification reaction of terephthalic acid (TPA) and ethylene glycol (EG) in the first tank reactor of TPA/EG continuous esterification, experiments at various addition rates of potassium titanium oxyoxalate were made in the pilot plant. Potassium titanium oxyoxalate accelerated the esterification reaction of TPA and EG. Also, reaction rate constants of the reaction scheme reported in a previous report were fitted with the experimental results, and the calculated values of physical properties of oligomers obtained from these reaction rate constants showed relatively good agreement with experimentally obtained physical properties of the oligomers. The effect of potassium titanium oxyoxalate on the reaction rate constants was expressed by a set of seven equations:

equation image

Using the resultant reaction rate constants, the esterification reaction at various addition rates of potassium titanium oxyoxalate were stimulated and the following conclusions drawn:

Under low pressure close to atmospheric, when the amount of water in the reaction mixture is very low, the decomposition of potassium titanium oxyoxalate proceeds slowly and decomposition can be practically neglected.
Potassium titanium oxyoxalate accelerates the esterification reaction.
Potassium titanium oxyoxalate mainly accelerates the main reactions and its effects on side reactions are rather weak. As a result, the higher the addition rate of potassium titanium oxyoxalate, the lower the values of AV and DEG, as is preferable.
Fully developed multilayer polymer flows in slits and annuli
Authors: Nordberg M. E. , Winter H. H. 
Published: December 2004

AbstractA numerical method has been developed for simulating fully developed multilayer shear flows of non‐Newtonian fluids with arbitrary viscosity functions. Poiseuille and combined Poiseuille/Couette flows in both slits arid annuli may be modeled. The method employs a finite difference system where grid points lie on streamlines and move to their correct positions as the solution procedure converges. Interfaces are easily handled as particular stream lines with the equation of motion replaced by a boundary condition. The method is stable for high interface viscosity ratios and readily handles a large number of layers. Many authors have employed power law models to model multi‐layer non‐Newtonian flows. We find that the power law is sufficient to predict pressure gradients and interface positions in most cases, but gives unrealistically flat velocity profiles, even when truncated at finite viscosity. Results are presented for the Carreau fluid and for the rubber‐like liquid with shear thinning via Wagner's strain functional.
Shrinkage of low‐density polyethylene film
Authors: Liu Tuomin , Harrison I. R. 
Published: December 2004

AbstractWhen blown films of low‐density polyethylene are heated above their melting point (Tm) they shrink to an unoriented state at a conveniently measurable, rate. Curves of contraction as a function of time have been measured at different temperatures ranging from 120°C to 200°C. The contraction curves for shrinkage in the machine direction obtained at different temperatures are superimposable by a lateral shift along the log‐time axis. A master contraction curve, a portion of the retardation spectrum, and the activation energy are obtained. Shrinkage data for low‐density polyethylene films with different thicknesses were analyzed and a correlation was found between contraction and dichroic ratio. This correlation indicates that thermal contraction data can be used as a qualitative measurement of orientation in low‐density polyethylene film.
Compensation effects in viscosity‐temperature dependence of polymer melts
Authors: Tanguy P. A. , Choplin L. , Hurez P. 
Published: December 2004

AbstractThe thermal dependence of the parameters of the Carreau A model of viscosity has been investigated for 13 polymeric resins. It was shown that the zero‐shear viscosity and the time constant obey an Arrhenius‐type law and that, for these parameters, compensation effects are exhibited. The shear‐thinning index was found to be fairly independent of temperature. An important consequence of a compensation effect is that only one determination of a parameter at a given temperature gives the complete temperature‐dependence of this parameter.
Photographed impact of continuous fiber composites
Authors: Moore D. R. , Prediger R. S. 
Published: December 2004

AbstractInstrumented falling weight impact is conducted on eight different continuous carbon fiber composites. During impact, photography of the tension surface of the specimens enables crack propagation to be monitored. One photograph per specimen is taken. Measurements of integral crack length is related to corresponding absorbed energies during impact. These results enable an apparent value of Gc to be determined. These are tabulated for the eight advanced composite samples.
Effect of fillers on the rheological behavior of thermoplastic 1,2 polybutadiene rubber
Authors: Bhagawan S. S. , Tripathy D. K. , De S. K. , Sharma S. K. , Ramamurthy K. 
Published: December 2004

AbstractThe influence of fillers like clay, silica, and carbon black on the rheological properties of 1,2 polybutadiene has been studied using a capillary rheometer. Silica filled compound exhibited the highest viscosity and clay filled compound the lowest viscosity at all shear rates. The effect of filler loading and temperature on the Theological behavior has also been studied. Smooth extrudates were obtained in most of the cases and die swell was lower for silica and carbon black filled compounds than for clay filled compounds. Rheograms of different 1,2 polybutadiene systems have been found to merge into a master curve using modified viscosity and shear rate functions that contain melt flow index as a parameter.
Fracture toughness of filled polypropylene copolymer systems
Authors: Fernando P. L. 
Published: December 2004

AbstractThe impact strength to stiffness balance of a toughened polypropylene copolymer was modified through the addition of mineral fillers. The stiffness was improved over the base resin value for all formulations. However, the impact strength exhibited complex behavior. The fracture toughness Gc calculated using the linear elastic fracture mechanics theory was indicative of the materials resistance to crack propagation. The Gc values were modified significantly with the addition of fillers and for some formulations was greater than the base resin value. The LEFM analysis indicates that this is due to an increase in the damage zone size rp where the energy absorbing mechanisms are concentrated. However, the specific energy absorbed per unit volume decreased with the addition of fillers. The total energy to fracture measured using unnotched samples was indicative of crack initiation and crack propagation energies. This upper bound value decreased for all formulations indicating a reduction in the crack initiation resistance, in the presence of stress concentrating heterogeneities in the filled systems.
A deformation induced order‐disorder transition in isotactic polypropylene
Authors: Saraf Ravi F. , Porter Roger S. 
Published: December 2004

AbstractIn this study, isotactic polypropylene (i‐PP) has been deformed by uniaxial compression to draw ratios up to 16×, and at draw temperatures from 30°C to 140°C. An order‐disorder transition in the crystals is observed at draw temperatures well above the stability limit, 70°C, reported for the disordered phase; Furthermore, this disordered phase (called smectic) is found to induce ductility and improve the efficiency of draw. The deformation induced smectic phase has been characterized using WAXS, DSC, and on‐line compression load versus draw ratio measurements. In consequence, a set of process conditions are offered to optimize draw. A mechanism for plastic deformation of i‐PP is also suggested, using the smectic phase as a probe.
Properties and phase separation of reaction injection molded and solution polymerized polyureas as a function of hard block content
Authors: Willkomm Wayne R. , Chen Z. S. , Macosko C. W. , Gobran David A. , Thomas Edwin L. 
Published: December 2004

AbstractA series of amine terminated polypropylene oxide based thermoplastic polyureas with hard segment contents of 30%, 50%, and 70 percent were synthesized via solution polymerization and reaction injection molding (RIM). Amine terminated polypropylene oxide (PPO‐NH2) of Mn = 2000 was used as the soft segment and 4,4′‐diphenylme‐thanediisocyanate (MDI) extended with diethyltoluenediamine (DETDA) as the hard segment. These polyureas are linear, amorphous, and phase separated. Polymers were characterized by gel permeation chromatography (GPC), differential scanning calorimetry (DSC), dynamic mechanical spectroscopy (DMS), small angle X‐ray scattering (SAXS), and tensile testing. RIM polyureas had significantly lower molecular weights than solution polymerized polyureas, but their mechanical properties did not suffer, RIM polyureas have poorer phase separation than solution polyureas as evidenced by DSC, DMS, and SAXS, especially at high hard segment levels. SAXS shows phase separation levels of up to 100 percent for low hard segment polyureas and down to 10 percent for high hard segment RIM polyurea. DSC found no evidence of a hard segment glass transition, and the evidence from DMS was inconclusive. In addition to polymer characterization, demolding behavior was studied. The 30 percent hard segment was always tough and elastomeric, while the 70 percent hard segment was always very brittle. The 50 percent hard segment showed the greatest variation in properties, ranging from very brittle to very though as mold temperature and in‐mold time were increased. Demold brittleness is explained by the presence of low molecular weight DETDA/MDI oligomers on demolding, which continue to react on aging.
Wire bond behavior during molding operations of electronic packages
Authors: Nguyen L. T. 
Published: December 2004

AbstractThis paper presents some modeling work on the behavior of wire bonds during a typical transfer molding operation. In order to fill up the small recesses in a production size mold, transfer pressures as high as 1.000 psi are commonly required. The large driving pressure is potentially harmful to the fragile wire bonds. Lit the worst case scenario, the highly viscous melt front may cause enough shearing action to lift off the wire bonds completely. More often, however, wire sweeping is reported as one of the major causes of shorts in devices where long interconnect wires are looped between bond pads. Several interdependent factors govern the extent of wire sweep in a mold cavity of arbitrary geometry. The dimensions of the cavity, for instance, dictate the velocity of the melt front profile with the corresponding flow stresses and shear rates. The location of the chip to be encapsulated similarly influences the plastic filing pattern. So does the configuration of the particular chip design (e.g. planar vs recessed lead frames). Naturally, the severity of the problem is also controlled by the nature of the wires used during the bonding. For example, wire sweep may be controlled to a certain degree by tailoring the wire modulus to offer resiliency and spring‐ back after the melt front has swept across, but prior to curing. Furthermore, a low drag coefficient would also be obtained if some measure of control on the shape of the wire (e.g. circular vs rectangular cross‐section) or the pro‐ file exposed (e.g. angle of orientation of the wires with respect to the flow) is exerted.
Application of thermogravimetric‐mass spectroscopy analysis for polymer characterization
Authors: Jones E. G. , Pedrick D. L. , Goldfarb I. J. 
Published: December 2004

AbstractA general description of the thermpgravimetric‐mass spectroscopy (TG‐MS) technique is presented. Advantages and limitations are discussed with respect to other mass‐spectral techniques, and a few examples of applications of TG‐MS to the study of the thermal degradation of polymers are given.
Experimental and mathematical treatment of transfer pot temperature for thermosets
Authors: Manzione L. T. , Poelzing G. W. , Progelhof R. C. 
Published: December 2004

AbstractThe heating and flow behavior of thermoset molding compound within the pot of a transfer molding process were studied with flow visualization experiments and a mathematical model. The flow pattern within the pot was found to be a stagnation point flow. The extrudate temperature was only 10°C–15°C above the preheat temperature, and it was relatively constant except for start‐up and termination transients. The chemical conversion of the extrudate was well below the conversion to gel for typical process conditions. Variations in pot diameter, preheat temperature, and pot temperature were also examined.
Chlorinated high density polyethylene. I. Chain characterization
Authors: Chang B. H. , Zeigler R. , Hiltner A. 
Published: December 2004

AbstractHigh density polyethylene has been chlorinated by three different methods: in suspension and in solutions of two different solvents. Carbon‐13 NMR and infrared analysis show that chlorination in chlorobenzene solution leads to statistically random distribution while chlorination in suspension gives highly blocky substitution. An intermediate distribution was obtained by chlorination in tetrachloroethane solution.