bluuebunny/crossref_metadata_2025 huggingface dataset:
Azidosilane polymer—filler coupling agent
Authors: McFarren Gerald A. , Sanderson Thomas F. , Schappell Frederick G.
Published: December 2004

This new coupling agent shows promise for use in reinforcing hydrocarbon type polymers, such as polyolefins and polystyrene, with glass fibers and inexpensive mineral fillers. Sulfonyl azide derivatives readily form durable bonds to many thermoplastics at normal extrusion and molding temperatures, without the use of peroxide or sulfur‐type curing agents. Alkoxy silanes, attached to the sulfonyl azide, hydrolyze in the known manner forming bonds to inorganic fillers. Using commercial compounding and injection molding procedures, 40 wt percent of mineral fillers containing 1 percentofan azidosilane coupling agent were incorporated in polypropylene. Very substantial improvements in tensile, flexural and heat distortion properties were obtained with little loss in impact strength. An initial evaluation in a filled polystyrene showed significant, but less dramatic, improvements.
The evaluation of internal cracking in polyurethane adhesives
Authors: Swanson Frank
Published: December 2004

In 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

A 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

New 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

An 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

A 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

Contact 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

The 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

Five 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

Several 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

Cold‐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

Experimental 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

This 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

The 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

A 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

The 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

Similar 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

The 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

A 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

The 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

In 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

Reinforcement 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.
Development of stress birefringence and flow patterns during mold fillin and cooling
Authors: Han C. D. , Villamizar C. A.
Published: December 2004

An experimental study was carried out to investigate the development of stress birefringence patterns of molten polymer during the mold filling and cooling operation. For this study, a rectangular mold cavity with glass windows on both sides was constructed, which permitted us to record on a movie film the changes in stress birefringence patterns in the mold cavity during the molding operation, using a circular polariscope. The mold was equipped with an automatic relay system which closes the shut‐off valve when the pressure in the mold cavity reaches a predetermined value. The mold was also equipped with both heating and cooling devices, so that either isothermal or non‐isothermal injection molding could be carried out. The mold temperature was controlled by thermistor regulated controllers. During the entire cycle of the molding operation, the mold cavity pressure was continuously recorded on a chart recorder, using a melt pressure transducer. The present study shows how molding conditions (namely, injection pressure, melt temperature, mold temperature) influence the distribution of stress birefringence patterns in a molten polymer while it is being injected into, and cooled in, a rectangular mold cavity.
Polymer flows dominated by high heat generation and low heat transfer
Authors: Pearson J. R. A.
Published: December 2004

This paper aims to review recent studies of the flow of non Newtonian (temperature and shear rate dependent) viscous fluids and to relate them to commonly encountered difficulties in polymer processing. The flows considered take place in narrow channels or pipes, and are dominated by viscous forces. Heat generation and temperature variations are taken to be the most significant aspects. A dimensionless formulation of the energy and stress equations is employed, thus bringing out the role of Graetz, Nahme‐Griffith and Brinkman numbers. These latter are introduced as ratios of temperature differences. Special consideration is given to the question of the stability of such flows.
Temperature effect on the electrical resistivity of metal/polymer composites
Authors: Nicodemo L. , Nicolais L. , Romeo G. , Scafora E.
Published: December 2004

In this paper the effect of temperature and filler content ϕ on electrical resistivity of styrene‐acrylonitrile polymer filled with iron or aluminium powders has been investigated. The resistivity of such composites decreases suddenly by several orders of magnitude at a critical volume concentration ϕc, which depends on the size distribution of particles and on thermal history. For filler content lower than ϕc, the resistivity decreases with increasing temperature, whereas for ϕ > ϕc there is a sudden increase in resistivity at temperatures near the glass transition temperature of the polymeric matrix. This effect is more pronounced than the previously reported data on other composite systems.
The distribution of lamellar lengths within a spherulite
Authors: Phillips P. J. , Sien Herbert P.
Published: December 2004

One of the problems to be considered in the application of the Halpin‐Kardos theory to crystalline polymers is the relation of the crystal length to the only related and measurable parameter, spherulite size. The number average crystal length has been computed for various two and three dimensional models for the crystallization process assuming heterogeneous nucleation. It was found that high values of crystallinity are consistent only with lamellae that are stacked in a parallel fashion. For these systems the number average lamellar length is 0.55 of the spherulite radius. Lower crystallinity polymers have an average lamellar length 0.3 to 0.5 of the spherulite radius, the actual value being determined by the radius. For spherulites of radius 1μm or greater, the size of the primary nucleus has no noticeable influence on the average lamellar length.
Mathematical and experimental determination of temperature, velocity, and pressure fields in flat molds during the filling process in injection molding of thermoplastics
Authors: Thienel P. , Menges G.
Published: December 2004

When injection molding thermoplastics, temperature, velocity and pressure distribution not only vary markedly over the mold cross‐section, but also along the flow path. Moreover, these parameters also vary with time. Using the example of a typical injection‐molding material‐high impact polystyrene—the distributions in the flat mold are calculated and discussed. It was possible to test calculations by means of comparative experimental tests in an injection molding unit with variable wall thicknesses and long flow paths. The purpose of these investigations is to give a better physical understanding of these complicated flow processes and to provide indications for optimum process control.
The rheology of polysulfone
Authors: Shaw M. T. , Miller J. C.
Published: December 2004

The viscosity‐shear rate functions for polysulfone (PSF) condensates ranging from 0.4RV to 0.95RV were determined using capillary rheometry, The most probable distribution of molecular weights of these resins allowed facile comparison with the polydisperse Bueche theory for viscosity, The agreement in shape of the viscosity function with theory was good but the data were displaced by a factor of 3 to 4 to higher reduced shear rate, a fairly common occurrence for melts. The high absolute value of PSF viscosity was explained with existing empirical correlations as a combination of low critical molecular weight and strong intermolecular interactions. The temperature dependence of viscosity was found to be close to that for polystyrene in the temperature range, Tg + 90 to Tg + 190°C. The die swell, end corrections, and melt fracture characteristics were also determined. The latter was found to occur at a constant wall shear stress of about 6 × 106 dynes/cm2 while the die swell and end corrections were found to be small.
The kinetics of fiber growth from flowing solutions
Authors: McHugh A. J. , Vaughn P. , Ejike E.
Published: December 2004

Data are presented for the longitudinal and radial growth rates of polyethylene fibers grown from high molecular weight solutions using a seeding method in Poiseuille tube flow. Results indicate growth is a two‐step process with the first step the formation of very thin untapered filaments ∼25 μm in diameter which grow very rapidly the full length of the capillary tube. The second step involves radial thickening of the filament into a tapered shape, the kinetics of which have been measured. The discussion includes an analysis of the rapid longitudinal growth and a critical comparison to earlier experiments in both Poiseuille and Couette flow. A possible growth mechanism is suggested to explain the high growth rates found in these experiments as well as the unusual growth observed earlier for Couette rotor growth. A discussion of some kinetic data for the radial growth process is also given along with preliminary results which indicate thickening may only occur in flow of extensional kinematics.
Effect of molecular weight on high pressure crystallization of linear polyethylene. I. Kinetics and gross morphology
Authors: Hoehn Harvey H. , Ferguson Raymond C. , Hebert Richard R.
Published: December 2004

Ten linear polyethylenes ranging from Mw = 4.9 × 104 to 4.6 × 106 were crystallized in a dilatometer at 0.51 GPa and 242°C and then cooled slowly. Volume vs time data were used to follow the kinetics of the crystallization. The dilatometer data for the isothermal part of the crystallization were fitted to the Avrami equation. The time exponent was independent of molecular weight and the average was n = 2.2. Electron microscopy of fracture surfaces showed that all of the polyethylenes crystallized in extended chain morphology. The crystalline order and maximum extended chain crystallite thickness decreased with increasing molecular weight. The dominant morphological feature of the crystallized high molecular weight samples was a strand‐like network superstructure. Attempts to stabilize the hexagonal structure formed in the isothermal part of the crystallization failed, and all specimens had only the usual orthorhombic crystal structure.
An electron microscopy study of the microfibrillar structure of deformed polyethylene spherulites
Authors: Tarín P. M. , Thomas E. L.
Published: December 2004

A quantitative analysis of the deformation of thin spherulitic polyethylene films was undertaken at the microscopic level with the aid of a gold marking technique. The deformation microstructure which developed was further characterized through the use of a gold decoration technique. The microfibrillar morphology was found to agree quite well with Peterlin's model of the microfibril. Changes in the sample morphology as delineated by the gold decoration, support the proposed mechanisms of the transformation of the folded chain spherulitic morphology into the microfibriliar morphology and the subsequent deformation of the microfibrillai structure.
Diffusion of vinyl chloride from PVC packaging material into food simulating solvents
Authors: Chan R. K. S. , Anselmo K. J. , Reynolds C. E. , Worman C. H.
Published: December 2004

Two models are used to describe vinyl chloride monomer (VCM) diffusion from poly(vinyl chloride) (PVC) packages to food simulating solvents. It was found that when the initial solid concentration in a PVC package is 0,35 ppm: (a) For poor solvents such as water and oils, VCM concentration in the solvent, Cl, theoretically will not exceed 20 ppb. (b) For strong solvents, the volume ratio of package solid/solvent should not exceed 0.1 in order to keep (Cl)max below 20 ppb. (c) It was demonstrated that thickness can be adjusted to give a Cl = 20 ppb at the time equal to the shelf‐life of the package. The method can also be used to calculate the initial concentration of VCM in a package which will give a proposed level of maximum Cl when the solvent and package geometry are fixed. VCM diffusion from PVC pressure pipe to pipe fluids was similarly analyzed.
Prediction of diallyl phthalate molding performance from laboratory tests III. Correlation of data from capillary extrusion rheometer, mechanical spectrometer and differential scanning calorimeter
Authors: Slysh Roman , Guyler Karl E.
Published: December 2004

The purpose of this work was to determine if capillary extrusion rheometer and mechanical spectrometer data can be used to predict the molding performance of a commercially available diallyl phthalate (DAP) compound. In addition, differential scanning calorimetry (DSC) curves of “good” and “bad” batches were statistically analyzed in order to determine if the DSC peak shape is related to the molding performance. It was found that the data obtained from all three techniques correlate very well with the molding behavior of the DAP material studied. Capillary rheometer and mechanical spectrometer results show that lower melt viscosities and lower curing rates are desirable for obtaining satisfactory molding performance. The mathematical moments analysis of DSC curves indicates that DAP batches which molded well give peaks of fairly high symmetry, while all peaks of “bad” batches are skewed to the left. The center of gravity of the former is at a higher temperature and the variance is smaller than the corresponding values of “bad” compounds.
Characterizations of poly(methyl methacrylate) for optical coating or thermal forming operations
Authors: Wen Walter Y. , Hauschild Danny L.
Published: December 2004

The bulk surface and thermal properties and chemical conformation of several poly(methyl methacrylate) samples have been characterized. The results of the analysis have correlated well with the suitability of the thermoplastic sheets for optical coating or thermal forming operation. Techniques for inspection of the plastic sheets appropriate for such special applications have been recommended.
The fatigue behavior of graphite fiber reinforced nylon
Authors: Dibenedetto A. T. , Salee Gideon
Published: December 2004

The fatigue lives of graphite fiber reinforced nylon composites were related uniquely to the tensile strengths of the materials. The distributions of tensile strength and fatigue life were measured and correlated with either two‐ or three‐parameter Weibull functions. For a specific population, there existed a unique relationship between the two cumulative distributions. Thus, if the effect of an environmental variable on the distribution of strength is measured, the effect on the fatigue life can be estimated. It was also found that the mechanism of fatigue failure was influenced by the technique of fabrication. Compression molded materials failed through an isothermal, brittle mode of fracture, while injection molded materials failed in a ductile, thermal mode.
The operating characteristics of twin screw extruders
Authors: Smith John M. , Janssen Leon P. B. M. , De Koning W. L. , Abeln P. P. J.
Published: December 2004

The operation of a twin screw extruder processing a powder or granular solid is reviewed. The operating variables of screw speed and barrel temperature profile interact with a number of design parameters— screw design, die geometry, feed zone geometry and with the material properties, in determining machine performance. The factors that determine output and pressure development are specified in a sequence of block diagrams. The dynamic response of an operating machine to disturbances in the steady state conditions is explained in the light of the established relationships and interpreted in conventional control theory terms. Attention is drawn to the importance of mixing in the chambers formed by the screw channels and of the residence time distribution in determining the quality of the final product.
Kinetics and flow of diallyl phthalate resins
Authors: Sundstrom Donald W. , English Michael F.
Published: December 2004

The analysis of molding operations for thermosetting polymers requires knowledge of the rheology and reaction rates of the materials. The purpose of this research was to measure kinetic and rheological data on diallyl phthalate resins and to integrate these results into models describing the flow behavior. The chemical kinetics of the curing reactions were derived from calorimetric measurements taken with a differential scanning calorimeter. The rheological data were measured with a mechanical spectrometer equipped with eccentric rotating discs. A model based on the theory of ideal rubber elasticity was used to correlate the elastic storage modulus with reaction time and temperature. For the region below the gel point, the dynamic viscosity exhibited a power law dependence on angular frequency and an Arrhenius dependence on temperature.
Free coating of viscous and viscoelastic liquids onto a partially submerged rotating roll
Authors: Middleman Stanley
Published: December 2004

Experiments are performed on the dynamics of formation of a liquid coating picked up by a cylindrical roll rotating partially submerged in a free bath. Data on coating thickness for Newtonian fluids are found to correlate according to T = H(ρg/μU)1/2 = 0.56 for fluids whose viscosities range from 0.11 to 33 poise. Data for strongly non‐Newtonian and Viscoelastic fluids (polyacrylamide solutions) can be forced to fit this correlation by defining an “equivalent coating viscosity.” It is clear that this defines a pseudo viscosity, because the “equivalent coating viscosity” is observed to increase with increasing roll speed. This suggests that strongly Viscoelastic fluids respond to the rapid deformation suddenly imposed in the dynamic meniscus near the pickup point in a distinctly elastic manner that alters the flow through the meniscus.
Determination of rheological parameters from parison extrusion experiments
Authors: Ajroldi G.
Published: December 2004

The parison extrusion and the effects of post‐extrusion swelling and sagging in the blow molding process have been studied by several authors and some qualitative relationships with rheological parameters have been attempted. The aim of this work is to show that, under some simplifying assumptions, the relevant rheological parameters—the swelling of the parison and its tensile compliance—can be directly determined from the viscoelastic analysis of the process. The reliability of the model has been tested by experiments carried out by the pinch‐off mold technique which provides the parison weight profile as a function of both previous extrusion history and mold closing delay. First of all it has been shown that the proposed model is suitable to represent the data. The swelling behavior shows the expected dependence on time and shear rate and the long‐time swelling data compare well with those determined by capillary extrusion experiments. It has also been found that the measured tensile compliance is of the same order of magnitude as that determined by conversion of tensile relaxation experiments; however, in the blow molding experiments the compliance of the parison decreases with increasing extrusion shear rate, i.e., by increasing the induced anisotropy of the polymer. As rheological examples, the performance displayed on both industrial and laboratory machines is discussed for three high density polyethylenes.
A simplified description of viscoelastic behavior of polymers as illustrated with biaxially‐oriented poly(ethylene terephthalate)
Authors: Titomanlio G. , Rizzo G.
Published: December 2004

A rheological model of solid polymers is proposed. Its mechanical analog is a parallel of a linear spring and a Maxwell element with variable viscosity. The viscosity of the dashpot is allowed to change with stress both directly, by an Eyring‐type mechanism, and through free volume changes according to the Doolittle equation. Predictions of the model reproduce many of the features shown, especially after yielding, by constant velocity stress‐strain, stress‐relaxation and creep data taken at room temperature on biaxially‐oriented poly(ethylene terephthalate) over a wide range of loading rates.
The operation of the rheovibron in the shear mode
Authors: Locati G.
Published: December 2004

This paper describes the use of the Rheovibron visco‐elastometer in the shear mode. A new self‐centering sample holder was designed allowing the evaluation of the real and imaginary parts of the shear modulus on low modulus materials such as polymer melts, uncrosslinked and slightly crosslinked elastomers, and elastoplastics.
Orientation effects and cooling stresses in amorphous polymers
Authors: Struik L. C. E.
Published: December 2004

This paper deals with two kinds of internal stresses in amorphous polymers. First, the internal stresses connected with molecular orientation are discussed. A framework is presented that describes the interrelations of the various orientation effects (anisotropy, birefringence, etc.) and their dependence on the thermomechanical history of the material. The second part of the paper deals with the residual thermal stresses generated by rapid inhomogeneous cooling through the glass transition range. These so‐called cooling stresses are well‐known in glass technology. The theory of the quenching of flat glass plates is described, generalized to objects of arbitrary geometry, and shown to be applicable to polymers. The practical importance of cooling stresses is discussed.
The water relaxation in polymers containing the amide group
Authors: Pezzin Giovanni
Published: December 2004

The low temperature water relaxation of synthetic polymers containing the amide group is usually attributed to the motion of a water‐polymer complex in the amorphous region. According to Puffr and Sebenda the complex is formed by water and amide group in the stoichiometric ratio 1.5. Elastin, an insoluble protein of vessels and ligaments, seems the ideal polymer for testing the model, being practically free of polar side groups and having a glass transition at 200°C, so that its “water peak” can be easily investigated. Calorimetric investigations show that the molar ratio for “bound water‐amide group” is indeed 1.5, as predicted by the model. The activation energy of the “water peak” is very close, for the “dry” protein, to that of nylons, but it decreases with increasing hydration to a limit of 9 kcal/mole. The results give additional support to the traditional interpretation of the polyamide beta relaxation and to the Puffr and Sabenda model for the interaction of water and amide groups in synthetic polymers.
The fracture mechanics of polymers at high rates
Authors: Casiraghi T.
Published: December 2004

Instrumented pendula have been applied to investigate the fracture toughness of some polymeric materials—homopolymers and composites—by fracture mechanics. The method is simple, and can be easily used for routine testing or research work. The load transducer is such that it allows the achievement of very accurate stress‐time curves. Data are reported which clearly show the dependence of Kc on speed, temperature, and molecular weight. Kc is the critical stress intensity factor. It has also been found that the Kc experimental values can be correlated with a peculiar feature of the fracture surface for the determination of the intrinsic value of Kc/1 by the use of both the Dugdale model and a simple graphic correlation.
Poly (alpha‐methylstyrene) as a processing aid for rigid poly (vinyl chloride)
Authors: Wilson A. P. , Raimondi V. V.
Published: December 2004

Poly (alpha‐methylstyrene) (PAMS) is a new approach to process improvement in rigid poly (vinyl chloride) (PVC)—the use of a low molecular weight polymer as a process aid. PAMS can reduce fusion time, melt viscosity and improve heat stability of rigid PVC compounds. The reduced melt viscosity allows the addition of fillers to PVC without adverse effect on extrusion rates. This polymer also improves the resistance to melt fracture and shear “burning” at high shear rates. When used within the optimum concentration range, physical properties such as tensile strength, Izod impact and heat distortion are maintained. In addition, PAMS gives, improved production rates in both pipe extrusion and injection molding processes without sacrifice in properties.
The appearance retention properties of poly (vinyl chloride) compounds during weathering
Authors: Isner James D. , Summers James W.
Published: December 2004

Damage to poly (vinyl chloride) (PVC) compounds due to thermal degradation during processing has an important influence on its subsequent weatherability. High melt temperatures and/or high residence times cause white PVC to become more yellow and colored PVC to fade and bleach more upon weathering. If high melt temperatures are used, then short residence times are needed to maintain excellent weatherability. In addition to careful consideration of extrusion conditions, stream‐lined equipment is necessary to produce extrudate of uniform thermal history. Also, relatively high thermal stabilizer levels help reduce thermal damage and, therefore, improve weatherability. Impact resistance is better retained when processing occurs at higher melt temperatures. A reasonable compromise between extrusion rate and temperature must be reached to provide for adequate color and impact retention.