bluuebunny/crossref_metadata_2025_split huggingface dataset:
The evaluation of internal cracking in polyurethane adhesives
Authors: Swanson Frank 
Published: December 2004

AbstractIn an evaluation of low modulus polyurethanes as adhesives, systems based on 1, 4 butanediol‐extended methylene diisocyanate polymer displayed a tendency to crack during cure. Cracking occurred when these systems were gelled at low temperatures in thin layers where adhesion places constraints on dimensional change. A test technique was developed that evaluates the tendency for polyurethane adhesives to develop internal cracks during cure. The test consists of casting the material between the walls of two eccentric beakers and observing the behavior of the system as cure proceeds. The 1, 4 butanediol‐extended methylene diisocyanate system was studied by systematically evaluating the influence of processing variables on cracking. The variables studied included curing agent to prepolymer stoichiometry, moisture content of the curing agent, effect of pre‐evacuating the prepolymer, the inclusion of additives such as silicone antifoam agent and silane coupling agents, and time/temperature cure conditions. The following factors were identified as being primarily responsible for cracking in these polyurethane systems: (1) the stoichiometry of the curing agent to the prepolymer, which must be held within a narrow range; (2) the water content of the curing agent which must be minimized; and (3) additives, particularly silane coupling agents, which enhance adhesion of the urethane to the container walls and also prematurely terminate chain extension.
New photoresists of cyclized butadlene polymers
Authors: Harita Y. , Ichikawa M. , Harada K. , Tsunoda T. 
Published: December 2004

AbstractA new photoresist composed of cyclized cis‐1, 4‐polybutadiene has been developed. The resist has much higher sensitivity on exposure to ultraviolet light than the conventional resist from cyclized polyisoprene. This new resist has no resist‐flow even at 250°C, and provides high resolution on baking at 200°C. Thermogravimetric analysis showed that the cyclized polybutadiene decomposes at temperature higher than cyclized polyisoprene.
Sensitive chlorine‐containing resists for X‐ray lithography
Authors: Taylor Gary N. , Coquin Gerald A. , Somekh Sasson 
Published: December 2004

AbstractNew resists containing chlorine to enhance absorption to PdLα X‐radiation at 4.37 Å have higher sensitivity than currently available high‐speed electron resists when used in a high‐throughput PdLα X‐ray exposure system developed by Maydan and coworkers. Of the three classes of materials examined the poly(chloroalkyl acrylates) have the best properties. The sensitivity and contrast of these negative resists are dependent on the amount of Cl present, the structure of the chloroalkyl side chain, the inclusion of reactive functional groups, and molecular weight. Contrast is found to decrease with increasing sensitivity achieved by either increasing molecular weight or incorporating more reactive glycidyl groups. We suggest that such behavior, which is not predicted by theories of radiationinduced crosslinking, has its origin in competitive formation of intramolecular crosslinks with the desired, intermolecular crosslinks. Poly(2, 3‐dichloro‐1‐propyl acrylate) has been investigated in greatest detail. Samples of this polymer requiring a dose of 7 mJ/cm2 for 50 percent of the initial resist thickness (2 min exposure) have been used successfully to wet etch 1 μm features into SiO2, Al and Cr and 2 μm features into phosphosilicate glass. It has moderate resistance to ion milling and good resistance to plasma etching with Freon‐based plasmas.
Interfacial phenomena between brittle and polymeric films
Authors: Chow T. S. , Penwell R. C. , Liu C. A. 
Published: December 2004

AbstractAn ovrerview of a new theory for describing interfacial phenomena in layered composites is presented. Relations are given for determining the adhesion of thin brittle films on flexible substrates, for determining residual strains resulting from drying solvent cast films, and for calculating thermoelastic strains in unsymmetric laminates. An experimental technique to measure the adhesion is discussed and values are obtained using experimental data. Residual strains are also calculated using the derived relations and solvent d in data.
Peel mechanics of adhesive joints
Authors: Gent A. N. , Hamed G. R. 
Published: December 2004

AbstractA review is given of the mechanics of peeling rupture of an adhesive joint, consisting of a flexible adhering strip peled away from a layer of adhesive. Attention is drawn to a number of anomalous results that cannot be accounted for solely, in terms of the thermodynamic work of formation of two new surfaces. The work of detachment is found to be generally much larger than the theoretically‐predicted amount. Moreover, the value obtained is greater for thicker layers of adhesive, and for detachment at a peel angle of 180° rather than at 90°. Also, it is found to increase with increasing thickness of the adhering strip, passing through a maximum value in some cases and then decreasing as the strip thickness is increased still further. All of these effects are attributed to dissipative processes, for example, plastic yielding, in one or both of the adhering layers as they are peeled apart. Some quantitative relationships are given for the additional peel forces arising from plastic yielding of the adherend or the adhesive.
Adhesion effects and performance of mass transfer equipment using teflon surfaces
Authors: Ponter Anthony B. 
Published: December 2004

AbstractContact angle data are reported for a number of pure and binary liquids residing on a polytetrafluoroethylene (PTFE) surface, measured under conditions simulating distillation, condensation or absorption. By comparing the wettability of such systems with the performance obtained under the same conditions for equipment employing PTFE heat or mass transfer surfaces, it is demonstrated that liquid‐solid adhesion plays a key role in determining the heat or mass transfer rates. It is further shown for a considerable number of industriallyimportant conditions that PTFE can give enhanced equipment performance over that obtained, using conventional high energy solid materials.
Viscoelastic properties of homogeneous block copolymers
Authors: Shen M. , Soong D. , Hansen D. R. 
Published: December 2004

AbstractThe molecular theory of Rouse‐Bueche‐Zimm has been modified to predict the viscoelastic behavior of homogeneous block copolymers. The model consists of beads and springs whose magnitudes correspond to the types of blocks in the polymer. Maximum relaxation times can be computed by this model. Viscoelastic data for poly(styrene‐b‐α‐methyl styrene‐b‐styrene), poly(α‐methyl styrene‐b‐styrene‐b‐α‐methylstyrene) and poly(styrene‐b‐α‐methyl styrene) were determined by stress relaxation methods. The results compare favorably with those predicted by the theory.
Glass bead‐filled polypropylene part II: Mold‐filling studies during injection molding
Authors: Schmidt L. R. 
Published: December 2004

AbstractFive glass bead‐filled polypropylene composites, which had been rheologically characterized, were used in mold‐filling studies to investigate the influence of rigid beads (0 to 26 vol percent) in complex flow fields. The two basic flows studied were simple shear flow in an edge‐gated, rectangular cavity and stagnation flow leading to diverging radial flow in a center‐gated, rectangular cavity. Pigmented tracer elements were used to illustrate flow patterns and to distinguish the skin‐core structure which is a consequence of the injection molding process.Despite the strong dependence of the rheological properties (both viscous and elastic) and physical properties (density, thermal conductivity, etc.) on bead volume fraction, the basic character of the polymer dominated the flow behavior of each composite and the flow patterns were unaffected by the beads. Injection pressures were increased with increasing bead fraction to maintain the same, constant volumetric flow rate (2.21 in.3/min) for each composite. Relative injection forces follow closely the relative viscosit trend.
Structural foam molding of incompatible thermoplastics
Authors: Throne James L. 
Published: December 2004

AbstractSeveral mixtures eof reground low density polyethylene (LDPE) and gencral‐purpose polystyrene (GPS) were, foam molded into structural foam plaques using a chemical blowing agent. Flexural strengths of test specimens cut from the plaques showed characteristic drop in value in the 50/50 mixture, but the modulus increases monotonically with GPS content. The data are consistent with those of Paul and co‐workers on compression molded specimens. An added benefit was found with low concentrations of GPS in LDPE, where no appreeiable weight loss was observed after 2h in an aggressive solvent, benzene. This is attributed to the protection afforded the GPS by the continuous LDPE phase.
Thermai treatment of cold‐formed poly(vinyl chloride)
Authors: Brady T. E. , Jabarin S. A. 
Published: December 2004

AbstractCold‐drawing poly(vinyl chloride) at 24°C increased the yield strength by 25 percent, modulus by 50 percent, and the ultimate strength by 100 percent. The onset of thermal shrinkage was reduced from 80°C (Tg) to 45°C. This thermal instability can be a significant disadvantage of cold‐forming for many applications. It is shown in this study that subsequent thermal treatment at 70°C (T < Tg) re‐establishes a shrinkage onset temperature of 80°C without reducing property levels. The structural changes associated with both orientation and thermal treatment were investigated using DSC, X‐ray diffraction and birefringence. Cold‐drawing produces molecular alignment as measured by birefringence and X‐ray. Thermal treatment of unstretched samples, as well as stretched samples under constraint and stretched samples unconstrained, always leads to a small reduction in free volume as revealed by a measured increase in enthalpy at Tg. However, this free volume change, produces a thermally‐stable oriented structure only when the samples are treated under constraint. Thermal treatment does not stabilize unconstrained samples. Rather it causes almost complete molecular relaxation and a reduction of physical property levels.
Injection molding in disk‐shaped cavities
Authors: Stevenson J. F. , Galskoy A. , Wang K. K. , Chen I. , Reber D. H. 
Published: December 2004

AbstractExperimental results together with predictions based on a numerical simulation are reported for the filling by injection molding of a center gated, disk‐shaped cavity with acrylonitrile‐butadiene‐styrene terpolymer (Lustran ABS Q714) and with polypropylene (Pro‐fax 6523). At a specified fractional fill, the output of a pressure transducer (Δπzz) near the sprue was measured and the clamp force (F) was obtained by. integrating the output of four pressure transducers over the projected area. A systematic study was made to determine the effect of the (1) material properties, (2) cavity thickness, (3) melt temperature in the barrel, and (4) injection rate on the measured and simulated values for the pressure transducer output and clamp force. For a given barrel temperature, cavity thickness and intermediate‐to‐high injection rates, the pressure transducer output and clamp force were found to be nearly independent of injection rate for ABS and to increase with increasing injection rate for polypropylene. As the injection rate approached zero, the pressure transducer output and clamp force increased because of the long time available for cooling the flowing melt. For ABS the simulated results were about 5‐25 percent higher than experiment, whereas for polypropylene they were about 10 percent lower than experiment when the viscosity model included solidification Flow instabilities were observed to occur at conditions where the pressure transducer output curve showed a marked upturn with decreasing injection rate.
Charpy tests on brittle polymers
Authors: Tak A. G. M. 
Published: December 2004

AbstractThis paper describes a simple miss‐spring model of Charpy's classical impact bending test. In this model, the mass represents the striker, and the spring the bent specimen. The stiffness of the latter is calculated from the formulas for static bending. The model has been tested by experiments on polymethyl methacrylate at room temperature. First, it is shown that the model correctly describes the effect of the dimensions of the specimen (span, width and thickness) on the fracture impact energy Secondly it is shown, that the fracture energy calculated from the measured fracture time agrees with the fracture energy determined experimentally. Third it has been found that the fracture energy in impact can be predicted by extrapolation of the results of slow bending tests at various deformation rates. Lastly, it has been proven experimentally that any stress waves generated by the impact of the striker have little effect on the measured fracture energy.
Rheology and wire coating of high atomic number metal‐low density polyethylene composites
Authors: Bigg Donald M. 
Published: December 2004

AbstractThe rheological properties of high atomic number metal‐low density polyethylene composites were investigated. Tungsten, tungsten carbide, and lead powders were studied at concentrations up to 10 volume percent. Viscosity‐shear rate, die swell‐shear rate, and melt draw down to break data were, determined as functions of filler type, filler concentration, and particulate size at 200°C. The viscosity data were found to fit the Einstein relationship over the range of filler loadings and shear rates investigated. Tanner's equation was used to calculate the first normal stress difference from the die swell data. The effect of the fillers on the predicted first normal stress difference was contrary to previously observed experimental evidence. Melt draw down to break data was found to be very sensitive to filler contamination and correlated quite well with wire coating experiments. During low‐speed wire coating runs coating quality was found to be seriously affected by small levels of contamination present in the fillers. Coating duality was determined by surface smoothness and uniformity.
Effect of additives on the melt elastic modulus of rigid poly(vinyl chloride) formulations
Authors: Gough Robert G. , Chen I‐Jen 
Published: December 2004

AbstractA factorial experiment shows that calcium stearate and paraffin wax significantly decrease the melt elastic modulus of rigid poly(vinyl chloride) formulations. It is also concluded the melt elastic modulus of PVC is not significantly affected by the presence of methyltin stabilizer, acrylic processing aids or polyethylene wax. The only significant interaction found was that between temperature and concentration of paraffin wax. A regression model was derived for shear storage modulus (G′) at a deformation frequency of 100 radians/sec. No significant correlation between G′ and critical shear rate for melt fracture was discernable.
Influence of composite film structure on reflectance of vacuum metellized plastics
Authors: Hoffman D. W. , Dickie R. A. 
Published: December 2004

AbstractThe reflectance of vacuum‐metallized plastic parts prepared using corrosion resistant metals such as chromium, nickel, and stainless steel is substantially less than that of electroplated chromium. Model calculations and data indicate that the use of a clear topcoat to protect the vacuum‐deposited metal layer is a major factor in reducing the observed reflectance. There does not appear to be a simple change in metal deposition process, film structure, or composition that can compensate for the loss of reflectance incurred by application of the topcoat.
Thermal expansion instability and creep in amine‐cured epoxy resins
Authors: Mark R. , Findley W. N. 
Published: December 2004

AbstractSimilar thermal expansion instabilities, consisting of isothermal, time‐dependent changes in thermal expansion after a rapid change in temperature, were observed in epoxy resins with different degrees of cross‐linking. Creep experiments performed at different stages of expansion show decreases in tensile creep rate with decreased expansion. The role of changes in moisture content as a possible cause of the dimensional instability is examined for epoxy resins and a highly cross‐linked polyurethane. Results indicate that the state of expansion is the primary cause of changes in creep rate rather than temperature or moisture content.
Optimalization of processing conditions for thermosetting polymers by determination of the degree of curing with a differential scanning calorimeter
Authors: Maas T. A. M. M. 
Published: December 2004

AbstractThe curing reaction of thermosetting polymers is accompanied by exothermal heat which has been measured with a differential scanning calorimeter. The Perkin‐Elmer DSC‐1 B was used for recording the curing behavior of a diallyl phthalate molding compound and two unsaturated polyester molding compounds. The residual heat of reaction has also been determined by a dynamic DSC scan of partly cured products made at various mold temperatures and curing times. It was thus possible to calculate the degree of curing and to dictate the optimum processing conditions for the indicated molding compounds. The interpretation of results leads to the conclusions that the DSC can be used to set specifications and to perform quality control for the molding compounds and that the most significant processing parameter is mold temperature.
The effect of filler packing fraction on plastics properties
Authors: Ferrigno T. H. 
Published: December 2004

AbstractA critical factor in the performance of fillers in plastics composites is the manner in which the particles pack together. This is called the packing fraction; the true volume occupied by a filler divided by its apparent total volume. The means for determining packing fraction and its effect on viscosity and physical, thermal, electrical and economic properties are outlined.
Silane treated alumina trihydrate: A new formulating tool for flame retardant polyester fiber reinforced plastics
Authors: Atkins K. E. , Gentry R. R. , Gandy R. C. , Berger S. E. , Schwarz E. G. 
Published: December 2004

AbstractThe high strength to weight ratio of glass reinforced plastics (FRF) combined with their fabrication flexibility has led to increasing use in new applications that no other materials could satisfy. FRF often replaces metals in traditional applications. Increasingly stringent flammability requirements have led to the use of alumina trihydrate filler, usually in combination with halogenated rosins. However, difficulties in compounding and fabrication often limit, the alumina trihydrate loading. This requires substantial increments of halogenated resin to meet specific flammability restrictions. In such composites, the price of the compound may be too high for a given application and one must often compromise substantially on both processing and physical property performance. Alumina trihydrate filled systems commonly suffer from poor glass fiber wet out and mold flow, with reduced strength and uniformity in fabricated parts. This paper describes how a unique silane pretreatment for alumina trihydrate permits bulk molding compound (BMC)/sheet molding compound (SMC) formulations to be developed with increased loadings of the filler, reduced filler wet out time, and improvements in glass dispersion, mold flow out, strength and uniformity of the composite. The paper also shows how the halogenated resin content of flame retarded systems may be minimized by the use of this silane treated alumina trihydrate.
The production of glass fiber‐reinforced poly(butylene terephthalate) on a continuous kneader
Authors: Stade K. H. 
Published: December 2004

AbstractIn poly(butylene terephthalate) based compositions, thermal degradation of the polymer matrix during processing has to be minimized to achieve quality products. Experience has shown a temperature‐residence time relationship, indicating that for mixing systems with high product temperatures, the residence time of the product has to be reduced to avoid excessive thermal degradation. The power density of the mixing system is related to the specific energy input and the residence time of the product. From rheology, the power density is also known for a simple shear deformation which can thus be used to characterize the shear intensity of a particular mixing process. Comparing two different mixing systems by their power density provides us with a qualitative better understanding why higher shear is permitted with lower residence time. From theoretical considerations it was found that for a temperature‐sensitive product, like PBT, the power density in the mixing operation can be further raised, taking into account that with shorter residence time a higher product temperature is permitted. Production‐scale test work was carried out on a 200 mm screw‐diameter continuous kneader to investigate the effect of running conditions and screw design on the thermal degradation of two different types of PBT. Results have shown that for the high‐viscosity PBT a linear relationship exists between product temperature and the viscosity retained upon compounding. In a two‐stage kneader only minor thermal degradation is encountered in the melting section, but conditions become critical in the mixing stage due to the viscosity increase after introducing the glass fibers to the melt. A new feature in compounding thermodegradable products is the addition of unmolten polymer into the mixing stage of the kneader since this leads to a reduction in the product end temperature and, consequently, thermal degradation of the matrix material. The limited results obtained so far indicate that an optimum exists as to the amount of pellets added. At a 15 percent level the product temperature was reduced by 20°C as compared to 10°C at 20 percent. An energy balance carried out on the continuous kneader indicates that because of the low melt viscosity approximately 30 percent of the energy put into the product in the melting section of the kneader originates from external heating. A rough comparison shows that the power density of a continuous kneader is twice that of a single‐screw extruder designed for compounding PBT, but, can be tolerated because of the considerably lower residence time in the former mixing system.
The reinforcement mechanism of fiber‐glass reinforced plastics under wet conditions: A review
Authors: Ishida H. , Koenig J. L. 
Published: December 2004

AbstractReinforcement mechanisms of fiber‐glass reinforced plastics (FRP) under wet conditions are reviewed with emphasis on molecular structures of glass/matrix interfaces. Included are studies on glass surface, the glass/coupling agent interface, silane coupling agents on glass surfaces as well as in solution, the coupling agent/matrix interface, extending to the interphase of particulate‐filled composites, and matrix resin. For a better understanding of wet strength of FRP, the structures under dry conditions are extensively, reviewed. The chemical bonding theory still dominates other reinforcement theories. The importance of other factors such as orientation of silane coupling agents and the restriction of matrix polymer conformations are also considered. Based on recent development in spectroscopy, molecular level research of the glass/matrix interfaces has been initiated in the past decade, yet only a few spectroscopic investigations on the function of water have appeared. It is concluded that the correlation between spectroscopic investigations and mechanical properties of a FRP is indispensable.