bluuebunny/crossref_metadata_2025_split huggingface dataset:
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

AbstractA 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

AbstractAn 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

AbstractPoly(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

AbstractSome 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

AbstractSurface 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

AbstractWithin 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

AbstractThe 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

AbstractThe 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

AbstractChemical 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

AbstractThe 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

AbstractIn 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

AbstractThe 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

AbstractDuring 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

AbstractModels 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

AbstractFatigue 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

AbstractViscous 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

AbstractA 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

AbstractA 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

AbstractPositive 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

AbstractThe 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

AbstractIn 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

AbstractThe 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

AbstractThe 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

AbstractTrifunctional 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

AbstractIn 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

AbstractTemperature 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.