bluuebunny/crossref_metadata_2025_split huggingface dataset:
Entanglement networks of 1,2‐polybutadiene cross‐linked in states of strain. V. Relaxation phenomena and calculations of entanglement trapping
Authors: Carpenter Rick L. , Kan Hsin‐Chia , Ferry John D. 
Published: December 2004

AbstractLinear 1,2‐polybutadiene is cross‐linked near its glass transition temperature by γ‐irradiation while strained in simple extension with a stretch ratio λo. After release, the sample retracts to a state of ease (λs). From λo, λs, and stress‐strain measurements in extension from the state of ease, the concentrations of network strands terminated by trapped entanglements (vN) and by cross‐links (vx) can be calculated. For vx/vN ≡ R′o > 1, retraction to the state of ease is rapid. For R ≃ 0.3 or less, retraction is slow and extends over many logarithmic decades of time scale. When an eased sample is stretched to λo where the cross‐links do not contribute to stress, the subsequent stress relaxation of the entanglement network toward equilibrium is also very slow if R′o is small. The slow timedependent processes are attributed to a high proportion of untrapped entanglements on dangling branched structures. The concentration of trapped entanglement strands, vN, can also be calculated from the equilibrium stress at λo. The fraction of trapped entanglements agrees rather well with the predictions of the theory of Langley.
Synthesis, characterization, and viscoelastic behavior of single‐phase interpenetrating polystyrene networks
Authors: Thiele J. L. , Cohen R. E. 
Published: December 2004

AbstractSingle phase interpenetrating polystyrene networks were synthesized using a room temperature photopolymerization method. Divinylbenzene was used for crosslinking both networks in most cases; a few IPNs were prepared using acrylic acid anhydride to provide labile crosslinkages in the primary network. The IPNs were characterized by means of equilibrium swelling in toluene. The results of these experiments closely approached the predictions of a swelling equation derived under the assumption that the two networks were elastically independent. Deviations from the swelling equation predictions could be explained in terms of contributions from internetwork entanglements. Small amplitude dynamic mechanical measurements indicated that the presence of the small amount (∼10 percent) of tight primary network chains had no perceptible effect on the linear viscoelastic properties.
A dynamic mechanical study of the curing reaction of two epoxy resins
Authors: Senich G. A. , MacKnight W. J. , Schneider N. S. 
Published: December 2004

AbstractThe curing behavior of two commercially formulated epoxy resins composed of the tetrafunctional amine dicyandiamide and with differing epoxy components, 4,4′‐bisglycidylphenyl‐2,2′‐propane and the tetraglycidyl ether of methylene dianiline, is characterized by dynamic spring analysis. This supported viscoelastic technique is well suited to the determination of the onset of gelation under isothermal conditions but the method is not useful for monitoring later stages of reaction when the resins become more rigid. The activation energy for the curing of the two resins is about 87 kJ/mole (20.7 kcal/mole). Rate constants for the first order curing reaction are given. Additional studies of films cured below the ultimate Tg show that two relaxations can be observed upon heating. The first relaxation occurs near the original isothermal cure temperature with a low activation energy, about 250 kJ/mole, whereas the second relaxation occurs near the ultimate Tg, under the conditions used here, with an activation energy of 500–650 kJ/mole. It is believed that these activation energies provide a unique method of characterizing the molecular mobility of epoxy resins at various states of cure.
Automated torsion pendulum analysis of the formation and properties of a polyphthalocyanine
Authors: Gillham J. K. 
Published: December 2004

AbstractThe cure and transitions of a C10 diamide phthalocyanine resin have been investigated by the torsional braid method. Two relaxations (T′ > Tg and T > Tg) occurring above the glass transition temperature (Tg) are shown to correspond to two relaxations which develop prior to vitrification on isothermal cure. They bear directly on processibility of the material. Also investigated was the coupling between a low temperature transition (∼ − 146°C/2.1 Hz) inherent to the material and a low temperature water‐induced transition (∼ − 76°C/1.9 Hz).
Fickian diffusion of alkanes through glassy polymers: Effects of temperature, diffusant size, and polymer structure
Authors: Chen S. P. , Edin J. A. D. 
Published: December 2004

AbstractDiffusivities D ranging over six orders of magnitude with values as low as 2 × 10−13 cm2/s have been obtained by a recently developed permeation apparatus, employing a gas‐flow method and a flame ionization detector; Log D for hydrocarbons in bisphenol‐A polycarbonate (PC) at 120°C is proportional to the square of the molecular diameter (d2) as given by the Lennard‐Jones 6–12 potential. This correlation holds even for the nonspherical n‐hexane molecule. The activation energy for diffusion is also linearly related to d2, with values of 9.5 and 23 kcal/mol for methane and neopentane in PC, respectively. Comparison of PC with two similar polymers of higher glass‐transition temperatures (Tg) indicates that our diffusion data do not correlate with the Tg of these polymers. The presence of subsidiary transitions, however, appears to enhance segmental mobilities, increasing the rate of diffusion of the hydrocarbons. The thermodynamic solubility of alkanes in glassy PC can be directly related to their boiling points, and in addition, their enthalpy of solution is linearly related to the heat of condensation of these permeants.
Oxygen transmission through highly crosslinked polymers
Authors: Gordon Gerald A. , Ravve Abraham 
Published: December 2004

AbstractHighly crosslinked polymers of varying structure were produced by the reaction of poly(glycidyl acrylate) (PGA) and methacrylate (PGM) with a variety of anhydride crosslinking agents: chlorendic (CA), glutaric (GA), maleic (MeA), succinic (SA), and polyrnalonic (pMnA) anhydrides. Topology was also varied by the use of a diluent and a comonomer in the backbone chain. Oxygen permeation measurements were made on these polymers coated onto a polypropylene film substrate before crosslinking. The crosslinking process greatly reduced the O2 permeability which, however, was dependent not only on the degree of crosslinking (yield of the crosslinking reaction), but also on the crosslink density, the chemical nature of the structural elements, and the topology of the polymer network. Thus the most impermeable coating (XPGA/CA) was made not from the stiffest and bulkiest components (PGM and CA), but by the reaction of the bulkiest anhydride (CA) with the more flexible polymer backbone chain (PGA). This is explained in terms of the need for chain flexibility to produce a crosslinked structure of optimum space filling character and network tightness.
Transport in oriented bottles made from polyester resin
Authors: Swaroop Naresh , Gordon Gerald A. 
Published: December 2004

AbstractOxygen permeation has been measured in flat sheet as a function of degree of orientation, and oxygen and water transport have been measured in oriented polyester bottles. O2 permeability in flat sheets decreases gradually with orientation on either side of an abrupt decrease by about a factor of 2 after moderate orientation. The bottles tested were all more highly oriented than that critical decree; no significant effect of orientation on water or O2 transport in bottles could be found. Only container intrinsic viscosity (IV) (which is determined by molecular weight, and is therefore a convenient measure of polymer degradation) was significantly related to the transport properties of the bottles. It was found that O2 transport is increased with increasing IV while H2O transport decreased. The explanation for these seemingly contradictory data can be found in the chemistry of degradation of the polyester.
Diffusion, swelling, and consolidation in glassy polystyrene microspheres
Authors: Enscore D. J. , Hopfenberg H. B. , Stannett V. T. 
Published: December 2004

AbstractThe effects of prior thermal and swelling history on the kinetics and apparent equilibria of subsequent n‐hexane sorption in monodisperse, submicrometer diameter, glassy polystyrene microspheres were studied. Repetitive sorption and desorption cycling was compared with continuous sorption and desorption experiments. The apparent equilibrium uptake of n‐hexane in preswollen samples decreased monotonically with the cumulative time under vacuum independent of the cycle frequency or the number of sorption‐desorption cycles. This consolidation was modeled as a first order relaxation process with a single characteristic relaxation time. “As‐received” samples swelled in the presence of the penetrant and the apparent equilibrium n‐hexane content increased monotonically with the time under n‐hexane. The Berens‐Hopfenberg diffusion‐relaxation model accurately describes the cyclic and continuous swelling behavior of the “as‐received” sample. At each temperature studied, a true equilibrium n‐hexane content was approached asymptotically for the preswollen and “as‐received” samples after sufficient time under vacuum or n‐hexane, respectively. Whereas the apparent sorption equilibria were controlled by the cumulative time under vacuum or n‐hexane for the preswollen and “as‐received” samples, respectively, the absorption kinetics are subject to a systematic variation which depends only on the immediate prior vacuum history of the sample. The temperature dependence of the kinetic and equilibrium parameters describing diffusion, consolidation, and swelling suggests a unified molecular interpretation of these diverse glassy‐state transport and relaxation processes.
Finite element solutions for flow in a single‐screw extruder, including curvature effects
Authors: Hami M. L. , Pittman J. F. T. 
Published: December 2004

AbstractSlow developed flow in an extruder channel has been set up as a two‐dimensional, variational problem using a helical coordinate system, thus avoiding the usual geometrical simplification. Continuity is enforced by an integral form of constraint, and solutions for isothermal, Newtonian flow are obtained by a finite element method for both shallow and deep, highly curved channels. The performance of the solution procedure as a function of Lagrangian multiplier is discussed. Convergence to correct solutions is demonstrated for the shallow channel case. Deep channel results are compared with analytic predictions, curvature corrected according to Booy. Further testing of deep channel results will be made against experimental data.
Mechanical properties of polypropylene‐low density polyethylene blends
Authors: Nolley E. , Barlow J. W. , Paul D. R. 
Published: December 2004

AbstractBlends of polypropylene (PP) and low density polyethylene (LDPE) were prepared by both batch mixing followed by compression molding and extruder compounding followed by injection molding. Compression molded PP‐LDPE blends were found to have very poor toughness, whereas extruded blends, injection molded without weld lines, were quite tough. Injection molded blend specimens with weld lines were found to be weaker and failed at very low elongations at break. A simple adhesion analysis is presented which explains well the weakness at the weld line expected for incompatible blends. Addition of an ethylene‐propylene polymer with residual ethylene crystallinity was found to be a more effective “compatibilizer” for blends deficient in toughness than a related copolymer with less crystallinity. This effect is attributed to the more block‐like character of the former which permits it to play more nearly the interfacial role required of the ideal blend compatibilizing agent.
Energy transfer and bond strength in ultrasonic welding of thermoplastics
Authors: Frankel E. J. , Wang K. K. 
Published: December 2004

AbstractThis paper describes an investigation into some fundamental aspects of ultrasonic welding of thermoplastics. A simple model was developed to characterize the temperature rise at the weld interface up to the glass transition temperature. Beyond this point, the temperature increases more rapidly and almost directly proportional to weld time. The rate of temperature rise increases with increase of amplitude of vibration. The correlation between weld strength and interface temperature was established using the method of dimensional analysis. It was found that the process can be optimized in terms of weld strength by monitoring the power input. There is an optimal load one can apply to achieve high weld strength. The overall efficiency of the process is rather low in terms of energy usage.
Hot plate welding of plastics: Factors affecting weld strength
Authors: Bucknall C. B. , Drinkwater I. C. , Smith G. R. 
Published: December 2004

AbstractWelded joints were made under a range of conditions in polypropylene, glass fiber reinforced polypropylene and poly (methylmethacrylate) bars. Melt flow in the weld was investigated by microscopy and by contact microradiography, and weld strengths were measured by tensile tests. The fracture toughness of the weld zone was determined by tests on double edge notched specimens. The study shows that weld strength is strongly affected by hot plate temperature, heating time and melt flow during welding. Insufficient heating or melt flow results in incomplete bonding. Excessive melt flow produces strong transverse orientation. Both reduce strength, but in different ways, which can be distinguished by fracture mechanics tests.
Experimental investigations of shear and elongational flow properties of polystyrene melts reinforced with calcium carbonate, titanium dioxide, and carbon black
Authors: Tanaka Hideho , White James L. 
Published: December 2004

AbstractShear and elongational flow measurements on polystyrene melts reinforced with small particles were carried out. The influences of loading level, particle size and surface treatment on shear viscosity, principal normal stress difference, and elongational viscosity were discussed. These systems exhibited yield values for both shear and elongational flow. Experimental values for the ratio of the tensile to the shear yield stress give satisfactory agreement with the predictions of the von Mises yield criterion. The yield value appears to increase with decreasing particle size and may be varied with surface treatment. The principal normal stress difference at fixed shear stress decreases with volume loading of particulates. The results are interpreted in terms of a system forming a gel due to interparticle forces, which is disrupted by a critical distortional strain energy.
Electron‐beam lithography of chlorinated polystyrenes with narrow molecular weight distributions
Authors: Feit Eugene D. , Stillwagon Larry E. 
Published: December 2004

AbstractPolystyrenes with narrow molecular weight distributions have been chlorinated with only slight broadening of molecular weight distributions to yield materials that are five to six times more sensitive to electron‐beam irradiation. The chlorinated polystyrenes are useful negative resists for electron‐beam lithography. At molecular weights of 3‐4 × 105g/mole, their threshold sensitivities to 20 keV electrons are 1‐2μC/cm2. Their lithographic contrasts are ≥ 1.5; in fact, > 2.0 for the narrowest molecular weight distributions. They compare favorably in these regards to polystyrenes of similar molecular weight characteristics. Lithographic relief images that are 80% of the original thickness of the polymer film can be formed at three to four times the threshold dose.The degree of chlorination ranged from 0.65‐0.76 Cl/monomer unit. The infrared spectra of the chlorinated materials resemble the spectrum for poly(4‐chlorostyrene). Elemental analysis indicated, however that some addition of chlorine had occurred. More extensive chlorination or chlorination of the higher molecular weight starting materials broadened the molecular weight distributions.The chlorinated material, a kind of poly(4‐chlorostyrene‐costyrene), is less sensitive than poly(4‐chlorostyrenc) prepared by addition polymerization by almost a factor of four.
Sensitivity and contrast of some proton‐beam resists
Authors: Brault Robert G. , Miller Leroy J. 
Published: December 2004

AbstractFifteen negative and four positive resists were tested to determine their proton‐beam sensitivity and contrast. The ratio of the required 20‐keV electron dose (QE) to the required 100‐keV proton dose (QP) ranged from a low value of 7.8 to a high value of 270. In general, the most sensitive resists had the lowest values of QE/QP. This result is explained as being due to incomplete coverage by reactive species at low proton doses because the incident protons are spaced too far apart. The product of QP and the weight‐average molecular weight (Mw) was almost constant for a series of narrow dispersivity polystyrenes over the Mw range of 20,000 to 2,600,000. This product was used as a figure of merit for comparing negative resists.
Evaluation of optics and resists for 3000 Å wavelength photolithography with a Perkin‐Elmer printer
Authors: Shankoff T. A. , Bruning J. H. , Johnston R. L. 
Published: December 2004

AbstractA Model 111 Perkin‐Elmer projection printer, with a 3100 Å exposure capability was evaluated for far‐UV printing. The improvement found in resolution at 3100 Å compared to 4000 Å was roughly proportional to the mean exposure wavelengths in the near and far‐UV as verified by electrical probe yield data of printed meander patterns. The processing latitude of various photoresists of the diazide type was found in the 1.0 μm and 2.5 μm line width range by electrically measuring the line widths of meanders etched into metal films using the appropriate resist mask. Exposures were varied continuously on individual wafers so that the resist linewidth change vs exposure could be determined using a minimum number of wafers. It was found that resists such as AZ‐2400 which pass much of the exposing radiation have better latitude than those that absorb most of the exposing radiation (HPR‐204, MPR). Some new, unconventional resists studied have even greater latitude than the diazide resists. Design compensations which have to be made for proximity and related effects at fine dimension are in the 0.1 μm to 0.2 μm range. Depth‐of‐focus for the printer studied seems to be adequate for careful work at 1.0 μm using 3100 A exposure. The overlay printing capability, which includes mask quality, operator error, and printer optics and stability, is within 0.25 μm from level‐to‐level.
Polydiallylorthophthalate resist for electron‐beam lithography
Authors: Yoneda Y. , Kitamura K. , Naito J. , Kitakohji T. , Okuyama H. , Murakawa K. 
Published: December 2004

AbstractPolydiallylorthophthalate, PDOP, of low molecular weight and low molecular weight dispersivity has been prepared and investigated as a negative resist for electron‐beam, X‐ray and ultraviolet lithographies. The resist polymers were prepared by a conventional fractional precipitation method. It has been found that a high resolution pattern is obtained by using a molecular weight of 1 × 104 and an Mw/Mn < 2. This gives a good solubility difference between the exposed and unexposed portions in the developer. Resolution is less than 1 μm without any scum. Sensitivity for 15 kV electron bourns is 4 × 106C/cm2; and for X‐rays (Al Kα) it is 100 mJ/cm2. Sensitivity for UV is 10 times that of poly(methyl methacrylate), and resistance for C3F8 dry etching is comparable to AZ‐1350J.
Influence of the Braid on transition temperatures as obtained by torsional Braid analysis
Authors: Hedvat Schowl 
Published: December 2004

AbstractTorsional Braid Analysis (TBA), like many other sample‐supported techniques, measures the transition temperatures of a polymer deposited on an elastic support. It is shown here that any polymer transition found by the location of the maximum in the log decrement Δ (or loss tangent tan δ) of a composite shifts to lower temperatures as the rigidity (or modulus) of the elastic support is increased. The magnitude of this temperature decrease is larger for transitions at which a composite has a larger support‐to‐polymer rigidity ratio. In general the above conclusions hold even with unsupported systems if the rigidity (or modulus) of the sample can be increased without interfering with the polymer domain under investigation, for example, by crosslinking one of two phases of microphase‐separated co‐polymers.
Experiments in extensive mixing in laminar flow. I. Simple illustrations
Authors: Ng Kwok Y. , Erwin Lewis 
Published: December 2004

AbstractSimple quantitative mixing experiments in well‐defined deformations clearly demonstrate the validity of previously derived equations relating deformation and mixing. A simple mixture of black and white polyethylene is studied by direct measure of striation thickness. The well‐known linear relationship in simple shear is demonstrated. By using a simple method for uniform reorientation, the second power relationship in shear once interrupted, the third power relationship in shear twice interrupted and the fourth power relationship in shear interrupted three times are demonstrated. In uniaxial elongational mixing of a silicone fluid, exponential dependence of mixing on strain is demonstrated.
Viscosities of molten polymer blends
Authors: Carley James F. , Crossan Stephen C. 
Published: December 2004

AbstractPairs of four thermoplastic resins, polystyrene, poly(methyl methacrylate), acetal homopolymer, and nylon‐12, were intensively melt‐blended in nine proportions from 0 to 100 percent. Capillary rheometry at 210°C was done on each blend; melt densities were also measured on most of them. The dependence of shear stress on Rabinowitsch‐corrected shear rate was accurately represented, for all the blends, by a simple empirical model. The dependence of viscosity, at particular shear rates between 5 and 1000 s−1, on blend composition was examined and we fitted two viscosity‐composition models to all the systems by least‐squares procedures. The character of the dependence of blend viscosity on composition varied widely for the five binary systems studied, two being monotonic over the whole range of shear rate, two exhibiting clear minima and one displaying mixed behavior, with both a minimum and maximum viscosity seen at shear rates near 250 s−1. The McAl lister three‐body model satisfactorily describes the viscositycomposition dependence in all five systems. A simpler blend rule was useful only in the monotonic systems, and even there it was inferior to the McAllister model.
Flow of carbon black loaded styrene‐butadiene (SBR)‐cis‐polybutadiene blends through capillary dies—influence of mixing and the location of carbon black
Authors: Lee Biing‐Lin 
Published: December 2004

AbstractThe flow behavior of carbon black loaded styrene‐butadiene (SBR)‐cis‐polybutadiene (BR) is investigated as a function of mixing and the location of carbon black. The blends consist of an 80:20 weight ratio of SBR and BR with the incorporation of 20 phr carbon black via three different schemes to control the location of carbon black in the individual rubber phases. These are: (A) free black mixing of the three components, (B) mixing of SBR‐black masterbatch with BR, and (C) mixing of BR‐black masterbatch with SBR. Dynamic Mechanical Analysis (DMA) was used to characterize carbon black distribution. The damping characteristics indicate that when carbon black is masterbatched into either one of the rubbers, it continues to remain incorporated in that particular rubber phase upon blending with the second rubber. The flow behavior is measured with an Instron capillary rheometer. The results indicate that the viscosity function of these blends is not sensitive to the mixing conditions. However, the elasticity is always, dependent on mixing. Elasticity is expressed as ΔPe/σ, where ΔPe is the entrance pressure drop from the Bagley plot and σ the shear stress. In general, ΔPe/σ of the blend decreases with increasing mixing.