bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of cryo‐ground rubber on melt flow and mechanical properties of polypropylene
Authors: Phadke A. A. , De S. K. 
Published: December 2004

AbstractThe influence of cryo‐ground rubber (CGR) on melt flow and mechanical properties of polypropylene has been investigated. Cryo‐ground rubber was incorporated in the polypropylene matrix (a) in powder form and (b) as masterbatch with natural rubber. Natural rubber was found essential as a dispersing agent. The loading of cryo‐ground rubber has no significant effect on viscosity at high shear rates (>61 s−1) but at lower shear rates (>61 s−1), viscosity functions change shape with increasing cryo‐ground rubber content. The dynamic mechanical properties revealed that polypropylene is thermodynamically incompatible with natural rubber and cryo‐ground rubber. Cryo‐ground rubber in the powder form shows poor adhesion to polypropylene matrix and, therefore, decreases the impact strength at higher loading. Addition of masterbatch of cryo‐ground rubber and natural rubber improves the impact strength of polypropylene.
The role of the latent image in a new dual image, aqueous developable, thermally stable photoresist
Authors: Feely Wayne E. , Imhof Joann C. , Stein Cynthia M. 
Published: December 2004

AbstractA new dual image, aqueous developable photoresist can be processed to yield either positive or negative images that are crosslinked and thermally stable to temperatures >300°C. Positive images have similar resolution and processing parameters to conventional positive novolak resists. Negative resists from this system have a number of new and interesting properties that surpass the capabilities of their positive counterparts. In addition to producing highly resolved submicron images, thick coatings of resist can be used to form images with high aspect ratios. By adjusting the exposure of the resist, images with inward sloping wall profiles can be realized. As a result of the images being crosslinked and Insoluble in the resist coating solution, images can be recoated and new images formed over the top of existing patterns to form structures. A hypothetical mechanism that suggests that resist defects caused by dust on the mask or photoresist surface can be reduced In negative mode processing is also presented.
Poly(alkenylsilane sulfone)s as positive electron beam resists for two‐layer systems
Authors: Gozdz Antoni S. , Craighead Harold G. , Bowdkn Murrak J. 
Published: December 2004

AbstractAlternating copolymers of sulfur dioxide and vinyltrimethylsilane (VTMS) and terpolymers with allyltrimethylsilane (ATMS) and 1‐butene have been synthesized by low‐temperature, free radical‐initiated polymerization. The co‐polymers with VTMS were soluble but hydrolytically unstable. Whereas the copolymer from ATMS was insoluble, terpolymers containing less than 75 mol‐percent ATMS (relative to butene) were soluble in a variety of organic solvents. Moreover, they were stable against hydrolysis and had good film forming properties. Their electron beam sensitivity was 1.5 °C/cm2 at 20 keV. and their contrast was ∼2. The terpolymers have been used as a top imaging layer in a two‐layer resist system to transfer half‐micron features into a 1.2μm‐thick Novolac planarizing layer by oxygen reactive ion etching (O2, RIE).
Differential scanning calorimetry investigation of curing of bisphenolfurfural resins
Authors: Patel Pradip S. , Shah Praful P. , Patel Shanti R. 
Published: December 2004

AbstractBisphenolic resins have been prepared by alkali catalyzed condensation of bisphenol‐F, bisphenol‐A, and bisphenol‐C, respectively, with furfural. The resin samples have been characterized by elemental analysis, dilute solution viscosity measurement, and measurement of number‐average molecular weight. Curing reactions of these bisphenolic resins with hexamine have been investigated by differential scanning calorimetry. The overall apparent activation energies for the curing have been found to be 24 ± 2, 34.2 ± 1.9, and 36.8 ± 2.3 kcal/mole for bisphenol‐F‐furfural, bisphenol‐A‐furfural, and bisphenol‐C‐furfural resin, respectively. The curing reactions have been found to follow an overall first‐order kinetics.
Simulation of reacting flow during filling in reaction injection molding (RIM)
Authors: Lekakou C. N. , Richardson S. M. 
Published: December 2004

AbstractThis paper deals with computer simulation of the filling stage of the Reaction Injection Molding (RIM) process for cavities of rectangular, cylindrical, and disc shapes. The computer model is in two parts: the main flow and the flow by the moving front. In the main flow part, the transient equations of axial momentum, energy and species conservation and also the continuity equation are solved numerically by finite‐difference methods using a moving, changing mesh. In the flow front part, which is quite novel, the transient (parabolic) vorticity, energy and species conservation equations and the elliptic streamfunction equation are again solved by finite‐difference methods. An important feature of both parts is that convection along and across the flow is included in all the transient equations. Results are presented for all three cavity shapes and those for rectangular cavities are compared with the experimental results of previous investigators.
Pressure losses in the packing stage of injection molding
Authors: Darlington M. W. , Scott A. J. , Smith A. C. 
Published: December 2004

AbstractThe pressure loss between the mold and the nozzle in the injection molding of bar and box moldings has been monitored. The pressure drop observed during filling of the mold is reduced during the packing stage but remains finite. This has been attributed in the literature to solidification of polymer across the cavity transducer and to melt relaxation phenomena. Experiments have been carried out with hot molds to prolong the packing stage at the expense of the ‘cooling’ stage. Under these circumstances the pressure drop is reduced but not eliminated. The observed pressure drop may be related to the viscosity of the melt and its dependence on pressure and temperature although strain‐induced crystallization and the pressure dependence of the melting point can confer effects similar to the cooling stage.
The effect of rolling orientation on the brittle‐ductile transition in polycarbonate fracture
Authors: Oh Hie‐Young , Kim Byung H. 
Published: December 2004

AbstractThe effect of orientation on the brittle‐ductile transition in rolled polycarbonate was examined. It has been believed that the brittle‐ductile transition is governed by the residual stress at low reduction and the orientation at high reduction. But, our experimental results revealed that the brittle‐ductile transition is caused by neither the residual stress nor orientation. It is proposed that the brittle‐ductile transition may be ascribed to the morphological change which is produced during plastic deformation on rolling.
A kinetic approach to multifunctional polymerization with cyclization
Authors: Kumar Anil , Misra Sanjay 
Published: December 2004

AbstractA kinetic model for the step growth polymerization of multifunctional monomers RAf valid up to the gel point has been presented which accounts for the intramolecular reactions. From the Jacobson‐Stockmeyer equation, the average rats constant for this step has been derived and is found to be chain length dependent. A computation scheme has been evolved by which the molecular weight distribution of the linear, branched as well as cyclized polymer can be determined up to the gel point. It is found that even though the molecular weight distribution of cyclic oligomers is little affected for the range of the values of the intramolecular rate constant (kc) studied, the average chain length μn and the polydispersity index p of the polymer formed are extremely sensitive to kc near the gel point. Numerical computations confirm that as the gel point is approached, larger polymer chains are formed which have a higher tendency to react intramolecularly. However, even at high conversions the number of the cyclic rings per polymer chain remains small, which is consistent with experimentally observed results.
A study on polymer blending microrheology: Part IV. The influence of coalescence on blend morphology origination
Authors: Elmendorp J. J. , Van Der Vegt A. K. 
Published: December 2004

AbstractThe influence of shear induced coalescence on the origination of morphologies in polymer blending processes is investigated both theoretically and experimentally. In the theoretical part a route is proposed to estimate the fraction of collisions between disperse phase domains in simple shear flow that result in an actual coalescence. It was shown that under polymer blending conditions this “coalescence probability” is only substantial if the polymer/polymer interfaces exhibit a high degree of mobility. In the experimental part, the phenomenon of gravity induced droplet/planar interface coalescence is utilized to show the high degree of mobility of molten polymer interfaces. Seoul experiments on the relation between domain size and disperse phase concentration in polymer blends prepared on a single screw extruder were carried out. For extremely low concentration (<½ %) the domain size could be predicted satisfactorily by means of Taylor's classical criterion for Newtonian liquids, while at higher concentration coalescence increased the average domain size manifold.
Bryce maxwell: Scientist, innovator, teacher
Authors: Boyer Raymond F. 
Published: December 2004

AbstractWe first discuss two scientific publications by Maxwell: a pioneering paper on the nature and kinetics of crazing on atactic polystyrene; and his development of a new mechanical spectrometer with a frequency range from 6 × 10−4 to 1.6 × 102 Hz, and storage and loss modulus obtained with it on atactic poly(methyl methacrylate). An informal association with Maxwell and his group starting in 1970 has permitted us to appreciate him as an inventor and an innovator with a broad impact on the polymer field; and also to follow him in his role of teacher/professor.
A new approach to capillary viscometry of thermoset transfer molding compounds
Authors: Blyler L. L. , Bair H. E. , Hubbauer P. , Matsuoka S. , Pearson D. S. , Poelzing G. W. , Progelhof R. C. , Thierfelder W. G. 
Published: December 2004

AbstractA new capillary rheometer incorporated in an instrumented transfer molding press has been developed. This rheometer is effective for determining the viscosity characteristics of thermoset molding compounds under both isothermal and typical molding conditions. In examples of the rheometer's utility, the power law indices of two commercial epoxy molding compounds have been determined to be approximately 0.7. Additionally it has been shown that preconditioning typical epoxy compounds at 47 percent relative humidity causes a viscosity decrease of about 40 percent owing to plasticization of the epoxy resin.
Characterization of mixtures of linear polyethylenes of ultrahigh and moderate molecular weights
Authors: Ueda H. , Karasz F. E. , Farris R. J. 
Published: December 2004

AbstractThe crystallinity, density, dynamic mechanical properties, (25 to 250°C, 11 Hz), and tensile properties at 25°C have been studied for two mixtures of ultrahigh‐molecular‐weight linear polyethylene (Mw = 2.0 × 106), abbreviated UHMWLPE, and moderate‐molecular‐weight linear polyethylene (Mw = 5.7 × 104), abbreviated LPE. These mixtures, which covered the entire composition range, had been prepared with differing solvent‐thermal histories. An enhancement of both crystallinity and density and an obvious synergism in tensile properties were observed for quenched films made from the mixture in which both components had been co‐dissolved. The data indicate that UHMWLPE and LPE can cocrystallize under given circumstances.
Chloroform transport in stress‐whitened polypropylene
Authors: Chau C. C. , Fear D. L. 
Published: December 2004

AbstractThe transport property of chloroform in undeformed and stress‐whitened polypropylenes was studied. The rate of penetration of liquid chloroform in whitened samples prepared by uniaxial stretching was slower than that of the undeformed material. In the whitened region, the process appeared to be Fickian diffusion, while in the undeformed material, it was a combination of Fickian and Case‐II. The diffusivity (at 50°C) in the whitened region increased about 8 times as the strain rate of stretching decreased from 0.67 to 0.033/min. The temperature dependence of diffusivity (ε = 0.67/min) showed an activation energy of 10.16 Kcal/mole. The whitening effect was greatly reduced as chloroform was absorbed; the final residual whitening after desorption increased with the rate of stretching as determined by transmission densitometry. For the undeformed polypropylene, Case‐II type of matrix relaxation contributed significantly to the total flux. The transport process was relaxation controlled at the surface: it gradually changed to Fickian diffusion behavior toward the middle plane. The flux contribution of relaxation across the thickness increased with the sorption time, and that of diffusion decreased. These observations seem to indicate that cold drawing impeded the deformation by swelling stress from occurring at the penetration front.
Crystallization kinetics of polyetheretherketone (peek) matrices
Authors: Velisaris Chris N. , Seferis James C. 
Published: December 2004

AbstractDifferential scanning calorimetry (DSC) and the density gradient technique (DGT) were used to determine, both isothermally and dynamically, the crystallization kinetics of polyetheretherketone (PEEK). The data were analyzed by a model utilizing, for the first time, two crystal nucleation and growth processes which were observed experimentally in a typical Avrami plot of the isothermal data. Thus, by modeling the data as two separate Avrami type crystallization processes occurring in parallel, both isothermal and dynamic data could be predicted with the same model constants. The first process provided an Avrami exponent of 2.5 and an onset temperature of 320°C. The second process displayed an Avrami exponent of 1.5 and an onset temperature of 342°C. The validity of this dual mechanism crystallization model was proven in practice by predicting with best fit model constants, a wide range of crystallinities of both neat and carbon fiber‐reinforced PEEK samples that had been made at different cooling rates from the melt.
Fracture surface characteristics of unfilled thermosets
Authors: Robertson Richard E. , Mindroiu Viorica E. 
Published: December 2004

AbstractMany of the features that cause the great complexity of the fracture surfaces of thermosets are suggested to have a simple explanation. These features include the “basic longitudinal texture,” “steps,” “welts,” “arrays of skewed cracks,” and the “stacked lamellar texture.” The explanation for their occurrence is based on the hypothesis of an instability of the propagating crack front that produces a “fingering” ahead of the crack.
Intermolecular interaction in polymer alloys as studied by crack healing
Authors: Kausch H. H. , Petrovska D. , Landel R. F. , Monnerie L. 
Published: December 2004

AbstractThe “method of crack healing” permits measuring the mechanical effects resulting from an interdiffusion of chain molecules across an interface. Having shown that in highly cross‐linked ruptured styrene‐acrylonitrile (SAN) a two‐stage healing mechanism is active, a similar phenomenon was expected in blends of polystyrene (PS) with a more flexible component such as poly(vinyl methyl ether) (PVME), or with a more rigid component such as poly(−2,6 dimethyl 1,4 phenylene oxide) (PPO). However, in both cases crack healing at a temperature 10 K above the respective glass transition temperature (Tg) was linear with the healing time to the power of 1/4 and slower than with pure PS. This unexpected observation is explained by analysis of the thermal and viscoelastic behavior of these blends and by the different contribution to the stress intensity factor resulting from the entanglements formed by the interdiffusing molecules.
Skin‐Core morphology and failure of injection‐molded specimens of impact‐modified polypropylene blends
Authors: Karger‐Kocsis J. , Csikai I. 
Published: December 2004

AbstractThe structure‐property relationship as well as the failure phenomena of injection molded polypropylene (PP) blends modified with ethylene/propylene/diene terpolymer (EPDM) and thermoplastic polyolefinic rubber (TPO) were investigated. Single and double‐gated tensile bars were injection molded by different Injection speeds. Microscopic studies on the failure behavior of knit lines were carried out using microtomed sections taken from the doublegated specimens. It was found that during injection molding, a skin‐core morphology is formed in both the continuous PP matrix as well as in the modified PP blends containing rubber particles of various deformation. The characteristics of the latter are in agreement with those described by the Tadmor flow model. The skin consists of a thin pure PP layer, whereas the subsurface layer contains more or less elongated rubbery particles due to the elongational flow at the wall. The deformation of the rubbery particles decreases, but their concentration increases with increasing distance from the skin towards the core. The deformed particles are oriented tengentionally to the flow front profile. Failure during tensile and tensile impact loading is initiated in the shear zone along the skin‐core boundary. This zone has a transcrystalline character and favors the formation of crazing. Final fracture of the bars depends, however, on how crazing and shear yielding simultaneously interact. Their interaction is a function of the average particle size of the dispersed phase. Above an average particle size of 0.6 μm, crazing is prevented by shear bands. For injection molding of PP/rubber blends a moderate injection speed is recommended, if the melt viscosities of the components are closely matched. In this way a pronounced dispersion gradient of the rubber particles across the plaque thickness is avoided. However, for the blends modified with rubber of high viscosity ratio and greater melt elasticity, use of higher injection speed is advantageous. Here, the higher shear stress field decreases the average particle size taken into the direction perpen dicular to the lead, since the cross section of the stronger deformed particle decreases.
Dynamic mechanical properties and morphology of polypropylene block copolymers and polypropylene/elastomer blends
Authors: Karger‐Kocsis J. , Kiss L. 
Published: December 2004

AbstractThe relation between the dynamic mechanical properties and the morphology of polypropylene (PP) block copolymers and polypropylene/elastomer blends was studied by dynamic mechanical analysis (DMA), light‐ and electron microscopy. The latter techniques contributed to an improvement in assignments of relaxation transitions in the DMA spectra. It was established that PP block copolymers had multiphase structure since the ethylene/propylene rubber phase (EPR) formed in the copolymerization contained polyethylene (PE) domains. An identical morphology was found in the case of PP/polyolefin thermoplastic rubber (TPO) blends. Impact modification of PP by styrene/butadiene block copolymers led to a multiphase structure, too, due to the polystyrene (PS) domains aggregated in the soft rubbery polybutadiene phase. In the semicrystalline polyolefinic and in the amorphous styrene/butadienebased thermoplastic rubbers, PE crystallites and PS do mains acted as nodes of the physical network structure, respectively. PP/EPDM/TPO ternary blends developed for replacing high‐density PE showed very high dispersion of the modifiers as compared to that of PP block copolymers. This fine dispersion of the impact modifier is a basic regulating factor of impact energy dissipation in the form of shear yielding and crazing.
Studies of dissolution phenomena in microlithography
Authors: Krasicky P. D. , Groele R. J. , Jubinsky J. A. , Rodriguez F. , Namaste Y. M. N. , Obendorf S. K. 
Published: December 2004

AbstractDuring the dissolution process, polymer in the glassy state is, transported into a dilute solution. In some cases, a transition layer can be measured using laser interferometry. This layer is seen as a difference in reflected light intensity between the bare substrate and the maximum during dissolution. When poly(methyl methacrylate) dissolves in methyl ethyl ketone, the layer is not detectable below a polymer number‐average molecular weight of about 30,000. The layer becomes more pronounced as molecular weight of polymer increases.
Characterization and control of interfaces in emulsified incompatible polymer blends
Authors: Fayt R. , Jerome R. , Teyssié P. H. 
Published: December 2004

AbstractInformation on the interfacial region in incompatible polymer mixtures can be gathered using various techniques including electron microscopy, thermal transition analysis, and more sophisticated methods such as nonradiative energy transfer (NRET). Selected examples are reported here to illustrate the exciting potentialities offered by diblock copolymer emulsifiers in controlling interfacial adhesion and devising high performance polymer blends.
Shrinkage analysis of forged ultra‐high molecular weight polyethylene parts
Authors: Gauvin R. , Nguyen Q. X. , Chalifoux J.‐P. 
Published: December 2004

AbstractSome engineering thermoplastics cannot be easily processed by injection molding because of their high viscosity. This is the case for Ultra‐High Molecular Weight Polyethylene (UHMWPE). Parts are either compression molded or machined from extruded shapes. Over the years, forging has been increasingly used to produce more or less complicated parts. Forging is a process in which a preform is subjected to bulk deformation in constraining dies, by applying heat and pressure, but with the polymer remaining in the solid (semi‐crystalline) phase. To fabricate acceptable mechanical components such as gears and sprockets, a close control of the operating conditions and a good prediction of shrinkage are necessary, For a better understanding, a study has been conducted on forged UHMWPE disks and gears. Parameters such as material and mold temperatures, dwell time, speed of forging and dwell pressure were investigated. Results show that material and mold temperatures are the most important parameters. For gears, optimization of processing conditions led to a shrinkage of ∼0.2 percent, measured on pitch diameter. The effect of post‐annealing at various temperatures is also reported.