bluuebunny/crossref_metadata_2025 huggingface dataset:
Scutoid mutation of drosophila melanogaster specifically decreases olfactory responses to short‐chain acetate esters and ketones
Authors: Dubin Adrienne E. , Heald Nathan L. , Cleveland Byrd , Carlson John R. , Harris Greg L.
Published: January 2005

A molecular‐genetic approach has been taken to identify genes involved in olfactory transduction in Drosophila melanogaster. Two independent lines of research led to the finding that the dominant Scutoid (Sco) mutation causes a diminshed extracellular electroantennogram response to the odorants ethyl acetate (EtAC) and acetone (AC). Sco flies showed about 4‐ and 2.5‐fold reduced responses to EtAC and AC, respectively, compared to Canton‐S wild‐type and sibling control flies lacking the Sco mutation when electroantennogram recordings were made from the proximal anterior third antennal segment. The responses to five other odors from three different chemical classes were unaltered. The maximum response to either EtAC or AC was decreased with no change in apparent affinity. Responses to short‐chain (but not long‐chain) acetate esters and ketones were dramatically affected at all antennal locations tested. Only in the proximal quadrants were responses to ethyl acetoacetate also reduced. Most Sco revertants tested had a normal olfactory response; duplications of the region including no‐ocelli partially suppress the Sco bristle as well as olfactory phenotypes. Sco adults had an impaired behavioral response to EtAC but not to banana or propionate. There was no effect of the mutation on larval chemosensory behavior or extracellularly recorded adult compound eye and ocellar visual responses. These findings suggest the involvement of Sco in an olfactory pathway in adults which is specific for short‐chain acetate esters and ketones. © 1995 John Wiley & Sons, Inc.
Importance of target innervation in recovery from axotomy‐induced loss of androgen receptor in rat perineal motoneurons
Authors: Al‐Shamma Hussien A. , Arnold Arthur P.
Published: January 2005

In adult male rats, axotomy of the spinal nucleus of the bulbocavernosus (SNB) motoneurons transiently down‐regulates androgen receptor (AR) immunoreactivity. The present study investigates the importance of target reinnervation in the recovery of AR expression in axotomized SNB motoneurons after short (up to 5 days) and long (1 to 6 weeks) periods of recovery. In the long‐term recovery experiment, animals were divided into two groups. In one, the two stumps of the cut pudendal nerve, which carries the axons of the SNB motoneurons, were sutured together immediately after axotomy. In the second group, the proximal stump was ligated immediately after axotomy to prevent target reinnervation. Axotomy of the SNB motoneurons caused a significant down‐regulation in AR immunoreactivity within 3 days. At 6 weeks, AR immunoreactivity was still depressed in ligated animals but had recovered to control levels in resutured animals. The recovery in the resutured group was coincident with the first signs of reinnervation of the target perineal muscles, although reinnervation seemed to lag behind AR immunoreactivity. SNB soma size was significantly reduced 2 weeks after axotomy and returned to control levels after 6 weeks of recovery only in the resutured animals. These findings suggest that the target perineal muscles play a role in the regulation of AR expression and androgen sensitivity in the SNB motoneurons, perhaps mediated by muscle‐derived trophic factors. © 1995 John Wiley & Sons, Inc.
A method for determining the melt elasticity in capillary flow
Authors: Han C. D. , Charles M.
Published: December 2004

A method for determining the melt elasticity is developed. The method requires the measurement of axial pressure distribution in a capillary and makes use of the extrapolated value of the pressure at the exit of a capillary, the so‐called “residual pressure.” The same measurement also provides data for determining the flow curve. Measurements were taken with polyethylene and polypropylene. The results are presented and discussed with particular emphasis on the application of the method to various ways of processing polymers.
Dimensional recovery of cold‐rolled polycarbonate
Authors: Rusch K. C.
Published: December 2004

The dimensional recovery of cold‐rolled polycarbonate was measured between 100 and 147°C, and compared to stress‐relaxation data. The strain‐recovery isotherms were superimposed to produce a master curve which could be represented by a distribution function, U(τ), termed the strain recovery spectrum. U(τ) is found to be nearly identical to the relaxation spectrum, H(τ), calculated from the stress‐relaxation master curve; and the shift in U(τ) as a function of temperature, WLF shift factor, is similar to that obtained from other viscoelastic measurements on polycarbonate. For the deformations studied, 25 and 50% reduction in thickness, the recovery behavior is found to be independent of strain (linear), suggesting that nonlinearity in a polymer glass results from large stresses, and not from large strains.
Solids conveying in screw extruders part II: Non isothermal model
Authors: Tadmor Z. , Broyer E.
Published: December 2004

Isothermal solids conveying theories have been developed in the past. However, due to friction, the surface temperature of the solid plug does increase. This change in temperature will strongly affect the temperature sensitive coefficients of friction and consequently also the pressure that develops. The surface temperature of the solid plug is also an important variable on its own because, when it reaches the melting point, the solids conveying zone is terminated. A mathematical model has been developed to calculate the temperature profile in the solid plug together with the strongly interacting pressure profile. Calculations indicate that high pressure in the solids conveying zone can practically be obtained only by very efficient cooling of the barrel in this zone.
Characterization of polyvinyl chloride. Part III. An alternative GPC method for measuring the radii of gyration, and the degree of long‐chain branching of polydispersed polymers
Authors: Chan Richard K. S. , Worman Charles
Published: December 2004

A method for measuring the unperturbed radius of gyration and the degree of long‐chain branching in Gaussian‐distribution polymers is proposed. Polyvinyl chloride (PVC) and polyvinyl acetate (PVAc) were selected to illustrate the method. It was observed that PVC samples prepared by homogeneous and heterogeneous polymerizations exhibit the same degree of long‐chain branching. This conclusion is supported by viscometric data. The polydispersity ratios (Mw/Mn) indicate that both types of polymerizations would yield a very small amount of total branching (long chain and short chain.) The calculated unperturbed radius of gyration of linear PVC samples was found to be 0.185 \documentclass{article}\pagestyle{empty}\begin{document}$ \left( {\frac{{{\rm \dot A}^{\rm 2} {\rm mole}}}{{{\rm gm}}}} \right) $\end{document}, and that of PVAc was determined to be 0.107 \documentclass{article}\pagestyle{empty}\begin{document}$ \left( {\frac{{{\rm \dot A}^{\rm 2} {\rm mole}}}{{{\rm gm}}}} \right) $\end{document}. The value obtained for PVC is shown to be in agreement with the value determined from the viscometric method as described in our previous work.
Tensile yield energy in glassy polymers
Authors: Macosko Christopher W. , Brand Gary J.
Published: December 2004

An activation energy theory of yielding in glassy polymers has been proposed by Starita and Keaton. It predicts a linear relation between energy to yield and test temperature. This concept was tested and found valid for five amorphous polymers; poly(methyl methacrylate), polycarbonate, polyarylsulfone, polysulfone and poly(vinyl chloride), in uniaxial extension at temperatures from 25°C to the glass transition. For extenstion rates of 0.2 in/min, yield energy was found to go to zero at Tg, as commonly determined by thermodynamic methods like dilatometry or scanning calorimetry. The effect of other extension rates, plasticizer and molecular weight appears to affect only the intercept much as Tg is affected by the same changes. The slope, or the ratio of thermal to mechanical energy efficiency in overcoming the flow activation barrier, is largely unchanged.
Solid‐state structure of melt blended incompatible polymeric mixtures involving poly(vinyl chloride)
Authors: Work James L.
Published: December 2004

Poly(vinyl chlorides) having different melt viscosities were melt blended with several different incompatible polymers using a two‐roll mill and a Brabender Plasticorder. The properties of the mixtures can be easily reproduced from batch to batch only if the viscosity of the components does not change during the mixing process. Within this limitation, the order of addition of the components during the mixture preparation does not have a significant influence on the mixture properties.

The shear storage modulus of the incompatible mixtures in the temperature range between the Tg's of the components varies with the difference in component viscosities at the temperature of mixing. The moduli of these mixtures are compared to moduli calculated using Kerner's equations. Based on this comparison it is concluded that in any incompatible mixture the component having the lower melt viscosity at the temperature of processing tends to form a continuous phase in the mixture. The greater is the viscosity difference, the greater is this tendency. The viscosity of one component relative to the other can be changed by changing the molecular weight of the components and/or the temperature of mixing.
Procedures for the evaluation of the long term strength of plastics and some results for polyvinyl chloride
Authors: Gotham K. V. , Turner S.
Published: December 2004

Some of the problems associated with the study of failure are reviewed and exemplified by results on two commercial grades of PVC. The whole range of failure phenomena, from crazing to fracture, and the effect of notches on durability is discussed. A test schedule involving minimum experimental effort for the evaluation and comparison of the long term durability of thermoplastic materials is proposed.
Exudation of an antioxidant additive from thin polyethylene films
Authors: Bair H. E.
Published: December 2004

Surface microscopy studies have revealed the phase separation and exudation of a phenol type of antioxidant [4,4′‐thiobis (3‐methyl‐6 tert. butyl phenol)] from polyethylene at concentrations of 0.08 percent by weight. The equilibrium solubility of the antioxidant in polyethylene was estimated to be less than 0.01 weight percent at room temperature.

About 70 percent of the antioxidant was expelled from a thin polyethylene film after storage for three days at 70°C. Since the initial concentration of the stabilizer is typically 0.10 percent of the polymer by weight, the antioxidant exudation can lead to a serious shortening of the expected life of the polymer. Prediction of lifetime by accelerated aging tests must account for the depletion of the stabilizer by exudation. The life of stabilized samples should be measured at concentrations which do not exceed the solubility limit of the antioxidant in polyethylene at its use temperature.
Screw horsepower dependence on screw speed and size—theory and experiment
Authors: Chung Chan I. , Nichols R. J. , Kruder G. A.
Published: December 2004

Within a normal operating range of extruders, it has been well established that the output increases nearly proportionally to the screw speed but the screw horsepower increases more than proportionally to the screw speed, making the screw HP difficult to predict. It has been also known in scale‐up of extruders that the output may be predicted with reasonable accuracy but the screw HP is difficult to predict. No sound theoretical or empirical method predicting screw HP in a scale‐up calculation has been offered heretofore. Since a screw performs solid conveying, melting and pumping (or metering) functions simultaneously, any theoretical analysis of screw HP has to consider all three extrusion theories; solid conveying theory, melting theory and pumping theory. In this paper, semi‐theoretical equations for predicting screw HP as a function of screw speed and size are developed. Experiments are conducted to test the utility of these equations and the implications of the experimental results on extrusion theories are discussed.
Rapid flexural creep and engineering analysis for product design of a propylene copolymer
Authors: Aloisio Charles J. , Cammons R. R.
Published: December 2004

The flexural creep compliance of a propylene copolymer was determined as a function of time and temperature using stresses of less than 700 psi. Equilibrium compliances of 2.82 × 10−5, 3.80 × 10−5, and 4.47 × 10−5 in2/lb at 75, 140, and 168°F respectively, are predicted. The data are used to characterize a flanged pressure chamber. Deflections due to flange opening deformation modes predicted for life times in excess of 40 years indicate the need for flange reinforcement.
Characterization of vinyl chloride‐propylene copolymers
Authors: Chan Richard K. S. , Worman Charles H.
Published: December 2004

The unperturbed radii of gyration, S02/M, of vinyl chloride‐propylene copolymers at different propylene levels have been determined by a GPC method. When the percent propylene of an unknown sample is evaluated by density measurements, the molecular weights can be calculated from GPC data through the use of S02/M. It is believed, in most cases, that the percent propylene and degree of polymerization are enough to characterize commercial samples of such a copolymer system. The effects of these two variables on intrinsic viscosity have been isolated.
Analyses for mechanical and electrical properties of epoxy resins used as potting compounds
Authors: Fountain Roger
Published: December 2004

Chemical batch‐to‐batch variations of an acrylonitrile‐modified epoxy potting compound were monitored by infrared spectroscopy and correlated to capacitance and hardness measurements of the cured product before and after exposure to high humidity. The reversion resistance of the cured material was dependent upon the amount of a carbonyl functionality in the uncured potting compound. This relationship is an approach to assess the reversion resistance of these types of potting compounds.
Azide photoresists for projection photolithography
Authors: Clecak N. J. , Cox R. J. , Moreau W. M.
Published: December 2004

The spectral sensitivity of bisazide sensitized rubbers has been extended to 5000Å by the addition of p‐azidocinnamylidene derivatives of cyclohexanone. The photoresists were suitable for projection exposure at 4050 and 4350 Hg lines. The photospeed of the compositions is enhanced by increasing the unsaturation of the polymer component. Speed increase could also be obtained by exposure of the films at elevated temperatures.
Factors affecting the sensitivity of e‐beam resists
Authors: Brewer Terry L.
Published: December 2004

In order to determine the effects of chemical structure on electron beam resist sensitivities, a series of polymers with different reactive components and additives has been investigated. The results, based on a larger number of exposures varying over five orders of magnitude, point out several interesting facts. The data indicate that the sensitivity of negative resists is not a linear function of molecular weight as previously supposed. Also, the negative electron resists tend to be more sensitive and cover a broader range of sensitivities than positive resists. The results further show that olefin and epoxy groups greatly enhance the crosslinking rate of these exposed polymers. However, additives, which are good energy transferring type sensitizers, have little effect on resist sensitivity. This last result is not surprising considering the nonselectivity of the exciting electrons.
Mechanical properties of certain oriented crystalline polymers
Authors: Starkweather Howard W. , Jordan Thomas F. , Dunnington Gordon B.
Published: December 2004

The yield stress is a simple function of the deformation ratio in the direction of testing for specimens oriented by uniaxial or biaxial stretching or rolling. Unless the yield stress increases more rapidly than in proportion to the deformation ratio, there will be instability during tensile creep under high loads. The relative merit of various polymers differs for creep and stress relaxation. Fatigue and bend recovery are also related to the molecular structure.
Polymer surface reflectance‐absorptance characteristics
Authors: Hallman J. R. , Welker J. R. , Sliepcevich C. M.
Published: December 2004

During an investigation of the time for ignition of polymeric materials under the influence of radiant heating, it was found that the polymer surface reflectance‐absorptance characteristics were a major factor in the variance of the ignition times. A subsequent research study was made of the reflectance‐absorptance characteristics of those polymers used in the ignition testing. Reflectance values were obtained over the wavelength of 0.3 to 2.5 microns using a double‐beam Cary model 14 spectrophotometer with an integrating sphere reflectometer and over the wavelengths of 1.0 to 10.0 microns using a Gier‐Dunkle Hohlraum with a Perkin‐Elmer spectrophotometer. Absorptance values were obtained by means of Kirchoff's Law,

Drawings and graphs are included which illustrate the test apparatus and type of data collected. A table of average absorptances of several polymers are given and listed according to the particular type of heat source used.

Average absorptances of the polymers over the monochromatic wavelength span of the heat sources were calculated using the equation

Mathematical analyses were developed and are presented for both the integrating sphere reflectometer and Gier‐Dunkle Hohlraum unit.

Drawings and graphs are included which illustrate the test apparatus and type of data collected. A table of average absorptances of several polymers are given and listed according to the particular type of heat source used.
A study of chain addition polymerization with temperature variations: I. Thermal drift and its effect on polymer properties
Authors: Biesenberger J. A. , Capinpin R.
Published: December 2004

Models of chain addition polymerizations have been analyzed for effects of reaction parameters on thermal behavior during reaction and, consequently, on properties of the polymer formed. Emphasis was placed on the investigation of thermal drift phenomena in particular. Several dimensionless parameters were identified and their role in predicting thermal behavior was established.
Nature of fatigue behavior and effect of flaw size in polystyrene
Authors: McMaster A. D. , Morrow D. R. , Sauer J. A.
Published: December 2004

Fatigue tests under reversed tension‐compression have been made on polystyrene specimens in both the unnotched and notched condition. For the notched specimens subject to a stress amplitude of 2500 psi, the log of the fatigue life was found to be a linear function of the log of the notch size. From the data, it was possible to determine an inherent flaw size for polystyrene subject to alternating loading and this value is compared to corresponding values obtained from static tests. Fracture surfaces were examined by scanning electron microscopy and the changes produced by notching are discussed.
Temperature fields in extruder dies with circular, annular, or slit cross‐section
Authors: Winter Horst H.
Published: December 2004

Viscous dissipation causes significant temperature increases in polymers while they are flowing through extruder dies. The development of the temperature field has been studied numerically using the dimensionless parameters Na and Gz. With the annular geometry (parameter: ratio of radii κ) the well known developing temperature fields in capillaries could be compared with the developing temperature fields in an annulus and in a plane slit. The shear dependence of the viscosity is described by a “power law” and the temperature dependence by an exponential function. A simple graphical method is suggested for estimating temperature fields in extruder dies, making use of the fully‐developed temperature field for very long dies as a reference state. For the demonstration of results, a power law exponent n = 0.4 has been chosen.
Limiting concepts in extensional flow
Authors: Marrucci G.
Published: December 2004

A characteristic feature of extensional flows is their potential capability of determining a stable, oriented structure in liquid materials containing elongated particles. With reference to flexible linear macromolecules, either in solution or as polymer melts, the limiting conditions under which such an oriented structure is actually possible are critically reviewed. It is seen that orientation can be obtained either when entanglements are present, i.e. when the polymer molecules form some sort of network, or, if the molecules behave entirely individually, only under very special circumstances. Further, if the objective is the “freezing” of the oriented structure in a partly crystalline, high‐strength material, the conditions become even more restrictive.
Development of an extrusion rheometer suitable for on‐line rheological measurements
Authors: Springer Paul W. , Brodkey Robert S. , Lynn R. Emerson
Published: December 2004

A new type of extrusion rheometer has been designed which employs dual slit geometry with a double valve. The double valve concept allows a change in flow rates through the slits, while the total extruder flow rate remains constant thus leaving extruder operating conditions unchanged. Electronic pressure transducers are mounted along the slit to record axial pressure distribution. Flow rates are measured by weighing polymer output and wall shear stresses are calculated from the axial pressure profiles. Exit pressures are derived from extrapolating the pressure profile to the slit exit and from this information the normal stresses can be determined.
Theoretical model for intermeshing twin screw extruders: Axial velocity profile for shallow channels
Authors: Wyman Charles E.
Published: December 2004

Positive displacement intermeshing twin screw extruders have been analyzed by a simple model for flow in the channel formed by the screw root and screw flights. The model considers the down channel flow to be a combination of drage flow resulting from the relative motion of the barrel and screw and pressure flow resulting from the positive displacement action of the device. The pressure flow in this situation is distinguished from pressure flow in a single screw extruder in that the pressure forces induce flow toward the die for the twin screw model rather than away from the die as in a single screw extruder. Comparison of the down channel shear rate profile of apositive displacement twin screw extruder with that of a single screw extruder with no net flow reveals that they are identical but inverted with respect to channel depth. The model presented does not consider leakage between the twin screws or the rotational motion of the second screw.
On mixing in polymer flow systems
Authors: Bigg D. M.
Published: December 2004

The mixing of polymers is an important subject which has received considerable and recent attention. This study shows that residence time distribution curves give information on the distribution of material along the primary flow direction, but do not quantify in polymer flow systems. Several polymer processing systems have been analyzed and the degree of mixing has been related to strain in each of these systems. Strain correlates directly with transverse mixing, which is the most important aspect of polymer mixing. Mixer design is shown to influence the amount of strain needed to achieve a specified degree of mixedness.
Recycling plastics by two‐shot molding
Authors: Donovan R. C. , Rabe K. S. , Mammel W. K. , Lord H. A.
Published: December 2004

In response to increasing ecological and economic pressures, a two‐shot molding process has been developed to recycle molding plastics. This process buries scrap plastic under a skin of virgin plastic in the molded part, resulting in a laminate that has the appearance of and similar mechanical properties to the skin material only. Two injection units and a special nozzle design are used to achieve the desired lamination. Theoretical and experimental studies have been conducted to determine the effects of parameters on the amount of scrap material that can be buried and its effect on impact strength. With conventional production molding dies, scrap plastic comprising approximately 40 percent of the total shot has been molded beneath virgin plastic in parts having stringent appearance requirements.
Treatment of structural foam testing results
Authors: Pramuk Paul F.
Published: December 2004

The great strides made over the last two decades allow the design engineer to predict performance characteristics in solid plastics. The current state of the art in structural foam is somewhat more primitive. Theories and basic design procedures as well as measurement of mechanical properties require evaluation. Because of the deep penetration of structural foam into the marketplace, especially in the large consumer areas of furniture and automotive applications, design techniques are required to cover the many application. This paper reviews briefly the basic information needed for structural foams, compares empirical relations and theoretical models, and discusses some inherent limitations of foamed materials.
Hydrostatic extrusion of polypropylene and properties of extrudates
Authors: Yoon H. N. , Pae K. D. , Sauer J. A.
Published: December 2004

The solid‐state extrusion of polypropylene by hydrostatic pressure has been investigated at four different temperatures: 25, 50, 75, and 100°C. The pressure to effect extrusion was found to be essentially a linear function of the extrusion ratio at each temperature, while the magnitude of the extrusion pressure, for any given extrusion ratio, decreased appreciably with increasing temperature. With increase in extrusion‐ratio, the polypropylene extrudates became increasingly transparent. After passing through the extrusion dies; the Sample showed some elastic recovery. The amount of this recovery decreased with increasing extrusion ratio, X‐Ray diffraction measurements taken before and after extrusion showed reduction in sharpness of the crystalline Peaks. Differential, scanning calorimetric measurements, on the other hand, indicate that the relative heat of fusion of the extrudates increases with the extrusion ratio at each extrusion temperature. It also increases with extrusion temperature for a given ratio. Tensile stress‐strain tests were made at various hydrostatic pressure levels on the extrudates obtained at 25°C and the extrusion ratio of 2.8. Unlike on the virgin sample of polypropylene, ho yield maximum was observed on the extrudate sample at all pressures investigated. However, the effects of pressure on the relative increase in the yield stress‐and the modulus of the extrudate are comparable to those of original, unoriented samples.
Rheological changes during a urethane network polymerization
Authors: Lipshitz Stephen D. , Macosko Christopher W.
Published: December 2004

Trifunctional poly‐ε‐caprolactone polyol was polymerized with a chain‐extended 1,6‐hexane diisocyanate, and the rheology followed by cone and plate flow. Viscosity was found to be independent of shear rate up to at least 102 N.s/m2 (103 poise) and 30s−1. Extent of reaction was monitored by a periodic titration for isocyanate groups. Using branching theory, viscosity was related to extent of reaction and temperature. Such relations should be useful for process models. Normal force data for the curing system are also reported.
New sources of monomers and polymers—A review
Authors: Seymour Raymond B.
Published: December 2004

In spite of the availability of‐ almost fifty commercial synthetic plastics, many new ones were announced at the recent First Chemical Congress of the North American. Continent at Mexico City. Among these are the high temperature resistant aramides and imides, poly(phenylene sulfide), poly(phenylene oxide), poly(aryl sulfone), H resin, modified phenolic resins and the phosphazenes. Other new polymers are block and graft copolymers, conductive polymers, barrier resins, poly 1,2‐butadiene, polyolefins and polyurethanes. New coupling techniques and shortages of feed stocks have resulted in a renewed interest in filled plastics and recycled polymers.
Temperature development in the leakage flow of screw extruders
Authors: Meyer H. E. H. , Housz J. F. Ingen , Gorissen W. C. M.
Published: December 2004

Temperature distribution at the exit of the leakage gap is of interest for a number of problems. For the calculation of temperatures, the leakage flow may be considered to be a pure drag flow to a good approximation. In the Newtonian case, thermal development length may be expressed in terms of gap height as L ≈ 3/8Pe · δ;usually this is less than the available gap length. Pe is the Peclet number and δ the height of leakage gap. Therefore the existing flow may be considered fully developed. For power law fluids, numerical calculations lead to results of the same order. Martin's results therefore may be applied to the flow at the exit of the leakage gap.
Corona‐discharge treatment of polyethylene films. I. Experimental work and physical effects
Authors: Carley James F. , Kitze P. Thomas
Published: December 2004

Corona treatment of films, mainly polyethylene, was studied at commercial levels in a small continuous treater. Degree of treatment was characterized by measuring polar and dispersion components of surface energy, ASTM Wipe and ASTM Adhesion Ratio (“peel adhesion”). The chief factors studied were corona current, applied frequency, web speed, dielectric thickness and air‐gap thickness between electrode and film. Other factors less intensively investigated were type of film, film additives, aging time after treatment, humidity and corona atmosphere. The polar component of surface energy, γ, is the key to understanding the changes in adhesive behavior of the films during treatment. We found that, for the equipment used, γ is accurately given by the equation

where D = dielectric thick ness and G = air gap, both in mils; S = web speed, ft/min; I = corona current, ma, and γ is in dyne‐cm/cm2. A similarly structured equation describes ASTM Wipe. Using measured surface‐energy components for the pressure‐sensitive tape used in the peel adhesion test, it was possible to calculate an adhesion interaction for each film on which peel adhesion was measured and to show that it closely correlates with peel strength. Humidity changes in the moderate‐humidity range, number of electrodes used and corona frequency had little effect on properties. Slip additives inhibited development of adhesion until treatment levels became high; adhesion properties gradually diminished upon aging of films stored at ambient conditions.
An upper bound on the performance of plane strain mixers
Authors: Erwin Lewis
Published: December 2004

Consideration of the basic equation for mixing in plane strain laminar flow shows that mixing can proceed much more rapidly than has been commonly accepted. While linear rates of mixing have been predicted previously, exponential rates of mixing are possible. An upper bound for, the rate of mixing in plane strain laminar flow is shown to be an exponential. The geometry of the flow which produces this most rapid mixing is shown to be plane strain extensional flow, sometimes called pure shear flow, with all interfaces aligned normally to the smallest principle axis of the deformation.
Dynamic‐mechanical behavior of poly(vinyl chloride), PVC, and chlorinated PVC compounds in the range of processing temperatures
Authors: Bonnebat C. , De Vries A. J.
Published: December 2004

Both real and imaginary components of the complex shear viscosity have been determined as a function of strain amplitude, frequency and temperature for various samples of poly(vinyl chloride), PVC, and chlorinated PVC of increasing chlorine content, with the aid of a Rheometrics mechanical spectrometer using eccentric rotating disk geometry. Different methods of sample preparation (low temperature dry‐blending, high temperature extrusion or calendering) were used to study thermomechanical history effects. Results obtained in the region of “linear” viscoelastic behavior were compared with those of capillary flow experiments: at relatively high temperatures the validity of the Cox‐Merz relationship was confirmed. Use of time‐temperature superposition procedures made it possible to predict the important variation of viscosity over a broad range of shear rates. The experimental results in particular with regard to the strong influence of temperature and thermal history, were tentatively interpreted in terms of a supermolecular structure due to the presence of ordered domains (microcrystallites) of variable amount and size. This interpretation was shown to be consistent with differential scanning calorimetry.
Rheological and energetic considerations of the fluid dynamics and scale‐up of mixing small particles into polymer melts in an internal mixer
Authors: White James Lindsay
Published: December 2004

A basic theoretical investigation is made of the fluid mechanics of mixing of particulates into a polymer melt in an internal mixer. It is shown how increasing levels of viscoelasticity, especially with non‐linear, strain rate hardening character, should deteriorate mixing. he characteristics of internal mixers are discussed in terms of dimensionless groups. Rational scaling procedures based on considerations of viscoelastic fluid mechanics and energy balances are critically investigated and their limitations considered.
Impregnated concrete. I: Characterization of poly (methyl methacrylate) prepared in concrete matrices
Authors: Madruga E. L. , San Roman J. , Fontan J.
Published: December 2004

Concrete specimens were impregnated with methyl methacrylate and after polymerization in situ, the extraction of polymer was carried out using appropriate solvents. The molecular weight and the stereochemical configuration of extracted polymer were determined by viscosity measurements and NMR spectroscopy respectively. The results obtained are discussed in relation to the increase of glass transition temperature of poly(methyl methacrylate) when the polymer is inside the concrete.
Analysis of impurity migration in plastic containers
Authors: Wang Fred H. L. , Duda J. L. , Vrentas J. S.
Published: December 2004

The problem of the migration of impurities from plastic containers has been analyzed, and the effect of the outward diffusion of the container contents on the impurity migration has been considered. The system of equations describing the coupled diffusion problem has been solved using finite‐difference methods, and an analytical solution has been developed for the initial stages of the mass transfer process. It was found that the outward diffusion of the container contents can exhibit a large effect on the migration of impurity if the ratio of the diffusivity of the container contents to the diffusivity of the impurity exceeds 100. Sufficiently large values of this diffusivity ratio and of the impurity partition coefficient can minimize the buildup of undesirable impurities in the contents of a plastic container.
Effect of polymeric additives on the rheological properties of talc‐filled polypropylene
Authors: Goel Dinesh C.
Published: December 2004

The effect of small amounts of low molecular weight polypropylene oxide on the rheological properties of talc‐filled polypropylene composites was studied experimentally using a capillary viscometer. The elastic behavior of the system was investigated by exit pressure and die swell methods. Initial studies showed that the talc filler does not influence the viscosity of the polypropylene but decreases the elasticity of the polymer system. Addition of oligomer concentration in a 40 wt percent talc‐filled polypropylene not only decreases the viscosity but also further decreases considerably the elasticity of the filled polymer composite. In both cases about 3 wt percent oligomer cone entration appears to be optimal, and further addition of oligomer does not significantly influence the rheological characteristics of the talc‐filled polypropylene composite.
A study of crosslinking in polyimides by viscoelastic and diffusion techniques
Authors: Chartoff Richard P. , Chiu Tai Woo
Published: December 2004

This paper is concerned with detecting crosslinking and changes in crosslink densities in cured polyimides. The methods used include diffusional weight gain and dynamic mechanical measurements on thin films of the cured polymers. In this study changes in diffusivities (D) for dimethylformamide (DMF) sorption into polyimide films as well as dynamic mechanical moduli and loss tangents are shown to be related to differences in polyimide cure schedule and composition. In all cases studied there is a β loss dispersion in the range 120 to 150°C and a γ loss dispersion in the range −50 to −80°C. The position and intensity of the β and γ relaxation processes vary primarily with cure cycle. There is a significant correlation between the magnitude of the diffusion coefficient and β and γ transition temperatures (Tβ and Tγ). Tβ increases and Tγ decreases with higher values of D so that T*, the difference Tβ − Tγ, is directly proportional to the diffusivity. By relating these results to data in the literature and the known curing behavior of polyimides, this trend is shown to be consistent with the presence of crosslinking and to be related to the crosslink density of the polymers. The data of this study indicate that measurements of diffusion coefficients for solvent sorption can be used to study changes in crosslink densities in glassy thermosetting polymers. Since the method is best suited for studying one dimensional diffusion, it also is suggested as a possibility for determining relative crosslink densities in adhesives bonded between substrates.
Sorption and transport of water vapor in glassy poly(acrylonitrile)
Authors: Stannett V. , Haider M. , Koros W. J. , Hopfenberg H. B.
Published: December 2004

Sorption data for H2O in glassy poly(acrylonitrile)(PAN) are presented for a range of relative vapor pressures at temperatures from 20 to 50°C. Simple dual mode sorption, involving “hole‐filling” and molecular solution appears to dominate the low activity region of sorption. Based on the clustering analysis suggested by Zimm and Lundberg, pronounced clustering of penetrant appears to occur above a relative pressure of 0.6. The form of the effective concentration‐dependent diffusion coefficient for H2O in PAN, determined by analysis of steady state permeation data, suggests that water in the microvoids and clusters has a lower mobility than the molecularly dissolved water in the polymer matrix. Time lag measurements at high upstream relative water vapor pressures suggest that the transient state permeation has a non‐Fickian character due to relaxations which occur slowly to accommodate the clustering process.
Manufacture of high stiffness solid rods by the hydrostatic extrusion of linear polyethylene. Part II: Effect of polymer grade
Authors: Hope P. S. , Parsons B.
Published: December 2004

The solid phase hydrostatic extrusion behavior of a range of linear polyethylenes, including methyl and butyl copolymer grades, has been compared in terms of processing behavior and product properties, for large diameter extrusions in the adiabatic thermal regime. The most useful improvements in both stiffness and long term creep behavior were obtained from medium melt flow index homopolymers, although such grades required higher forming pressures than the copolymers. This represents a reversal of the creep behavior trends observed for small diameter isothermal extrusions, where copolymer grades were superior. The engineering potential of hydrostatically extruded linear polyethylene is discussed.
Crystallization—morphology—polymer processing correlations for IUPAC low density polyethylenes
Authors: Magill J. H. , Peddada S. V. , Mcmanus G. M.
Published: December 2004

The crystallization behavior of three IUPAC low density polyethylene samples has been characterized by thermal analysis. Their rates of crystallization only are directly correlatable with their film forming ability in film blowing technology. The IUPAC samples possessed essentially indistinguishable physical properties, including differential scanning calorimetry (DSC) melting curves and rheological characteristics, but their propensity for crystallization was found readily to parallel their film forming ability and other characteristics associated with end‐use performance. The application of thermal analysis to assess crystallization is a unique diagnostic tool for measuring polymer film processability, which is well illustrated here using a few simple experiments made on the original polymer specimens and a polymer blend. Although all samples exhibit similar small‐angle X‐ray periodicities, the morphological differences assessed, particularly by microtomy‐optical microscopy, correlate with, and complement, the results of phase transformation kinetics responsible for film properties. Fractography‐scanning electron microscopy proves to be inferior to optical methods for revealing the morphology of these low density polyethylenes.
Energy‐related failure criteria of thermoplastics
Authors: Brüller O. S.
Published: December 2004

Three aspects of the failure of thermoplastics, having a special importance in engineering, are investigated. They are: (a) Transition from linear to nonlinear viscoelasticity; (b) Crazing; (c) Fracture. Energy related criteria, developed from the Reiner‐Weissenberg thermodynamical theory of strength, are used for the characterization and prediction of failure under its different forms, for simple uniaxial loading histories such as creep, stress relaxation and constant rate of strain. The computation of the stored and dissipated parts of the specific stress energy becomes possible in a relatively simple way, if the relaxation modulus and the creep compliance are approximated by Prony‐Dirichlet‐type series with a finite number of terms. Published experimental data, as well as experiments carried out by the author on different thermoplastics are in very good agreement with theoretical results. Further, based on experimental data, the equations obtained can be reduced to very simple and useful relations. The influence of elevated temperatures (below the glassy‐transition point) on failure is also considered.
Die drawing: Solid phase drawing of polymers through a converging die
Authors: Coates P. D. , Ward I. M.
Published: December 2004

Die drawing, a new process for the production of oriented thermoplastic rods with an ultrahigh modulus of elasticity, involves drawing an isotropic workpiece through a converging die at temperatures below the polymer melting point. Die drawing of polypropylene is described, but the process is applicable to any polymer which can be drawn by conventional means. The considerable advantages of die drawing compared with conventional tensile drawing and hydrostatic or ram extrusion are discussed.
Some studies on plasma polymerization of benzene and cyclohexane in the gas phase
Authors: Bölük M. Y. , Akovali G.
Published: December 2004

The glow discharge polymerization benzene and cyclohexane at 13.56 mHz, and 60 watts, in a plug flow reactor with inner electrodes was studied. Film powder and oily polymeric products were obtained from benzene, and only films were produced from cyclohexane. Polymers produced were analyzed by infrared and their characteristic maps demonstrating the correlation between various physical forms of polymer and reaction conditions were prepared. Excepting oily products, all others are found highly crosslinked and contained free radicals. Contrary to the plasma polymerization (PP) oil of benzene, all others showed no aromatic character.
Craze healing in polymer glasses
Authors: Wool R. P. , O'Connor K. M.
Published: December 2004

Craze healing was observed in many amorphous glassy polymers. A detailed study of the kinetics of craze healing in atactic polystyrene (Mw = 255,000) was conducted. The crazes were created in 0.08 mm films in air at room temperature, To, and constant stress, σo ⋍ 2,300 psi, healed at temperature Th for a time, Th, at σ = 0, and recrazed at To and σo. Nucleation times, τ1 and τ2, and growth rates, L1, and L2, for the first and second loading, respectively, were measured as a function of th and Th for individual crazes using dark field optical microscopy. Complete optical and mechanical healing was observed for Th ⩾ 70°C(Tg ≅ 100°C). At constant Th, healing progressed in five stages with increasing th as follows; (i) no healing, τ2 = 0, L2 ≫ L1; (ii) partial healing, τ2 <τ1, L2 > L1; (iii) similar growth, τ2 = τ1, L2 = L1; (iv) slower growth, τ2 > τ1, L2 < L1; (v) disappearance, τ2 → ∞, L2 → 0. A craze healing envelope of Th vs Th was obtained for the above stages. Craze healing occurred by line mode in which uniform healing occurred along the entire length of the craze.
Aging of pressure‐sensitive adhesives I: Stability of styrene‐lsoprene‐styrene block copolymer films at 95°C
Authors: Harrison Daniel J. P. , Johnson Julian F. , Yates W. Ross
Published: December 2004

This paper is the first in a series investigating the aging of pressure‐sensitive adhesives based on styrene‐isoprene‐styrene (SIS) block copolymers. An investigation of thermal/oxidative aging of thin SIS films is presented. During these aging experiments, samples were analyzed with size exclusion chromatography (SEC), multiple internal reflectance (MIR) infrared spectroscopy, tack tests, and surface tension estimations.
On the dynamics and control of a plasticating extruder
Authors: Costin M. H. , Taylor P. A. , Wright J. D.
Published: December 2004

In recent years, there have been many papers published on the application of process control to plasticating extruders. Much of the literature concentrates on the more classical control techniques. However, recent research has studied the application of stochastic identification techniques for building transfer function models for the extruder. In particular, the relationship of screw speed to die pressure and temperature has been studied. In the present work, both step tests and pseudorandom binary sequence tests were used to study the process dynamics of a 38 mm Killion extruder having a Iength‐to‐diameter ratio of 24:1. This study concentrates on the regulation of the extruder pressure in the face of its inherent surging characteristics. Variations in the quality of the feed plastic were studied through pulse and step changes in input polymer composition. Significant control problems resulted from measurement noise, which appeared at the same frequency as the screw rotation speed. Various mathematical filters to reduce the effect of this noise on the control variables were studied.