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Articles 31 - 60 of 149
Full-Text Articles in Engineering
The Effects Of Low Molar Mass Diluents On The Microstructure Of Ionomers, Robert Weiss
The Effects Of Low Molar Mass Diluents On The Microstructure Of Ionomers, Robert Weiss
Robert Weiss
The effect of polar and nonpolar low molar mass diluents on the microstructure of lightly sulfonated polystyrene (SPS) ionomers was studied using electron spin resonance spectroscopy, small-angle x-ray scattering, and dynamic mechanical analysis. Nonpolar diluents primarily affected the hydrocarbon - rich phase, while polar diluents partitioned into the ion-rich regions and disrupted the supramolecular structure. The ionic clusters remained intact, even at elevated temperatures, upon the addition of nonpolar solvents such as dodecane and dioctylphthalate. More polar solvents such as methanol and glycerol swelled the ionic domains and promoted increased mixing of the two phases.
Morphological Characterization Of Blends Of Metal-Sulfonated Polystyrene And Methylated Polyamide By Solid State Nmr, Robert Weiss
Morphological Characterization Of Blends Of Metal-Sulfonated Polystyrene And Methylated Polyamide By Solid State Nmr, Robert Weiss
Robert Weiss
No abstract provided.
Phase Behavior And Specific Interactions Of Blends Of Nylon 6 And Sulfonated Polystyrene Ionomers., X. Lu, Robert Weiss, T. K. Kwei, Y. K. Dai
Phase Behavior And Specific Interactions Of Blends Of Nylon 6 And Sulfonated Polystyrene Ionomers., X. Lu, Robert Weiss, T. K. Kwei, Y. K. Dai
Robert Weiss
No abstract provided.
Assessment Of Time-Temperature Superposition Of Linear Viscoelastic Behavior Of Strongly Interacting Polymer Blends: N-Methylated Nylon 2,10 And Lightly Sulfonated Polystyrene Ionomers, Robert Weiss
Robert Weiss
The applicability of time-temperature superposition of dynamic mechanical data for miscible polymer blends that exhibit strong intermolecular interactions was investigated. Blends of the lithium salt of lightly sulfonated polystyrene ionomers (Li-SPS), 9–12 mol% sulfonation, and N-methylated nylon-2, 10 (mPA) were miscible over the composition range studied, 30–70 wt% ionomer. Time—temperature superposition (TTS) of the storage and loss shear moduli measured at frequencies of 0.01–500 rad s−1 was applicable over the temperature range from 95 to 185°C. The molecular-weight distribution of the ionomer had no effect on the applicability of TTS. The success of TTS was attributed to the complexation of …
Studies On A Diphenylether Modified Poly(Phenyl-1,4-Phenylene Terephthalate) Liquid Crystalline Polymer And Its Blends With Polycarbonate And Polysulfone, Robert Weiss
Robert Weiss
Blends of a thermotropic liquid crystalline polymer, LCP, (4,4′-dicarboxy diphenyl ether modified poly(phenyl-1,4-phenylene terephthalate)) with polycarbonate and polysulfone were prepared and characterized with respect to their thermal properties, viscoelastic behavior, processability and mechanical properties. The processability of the thermoplastics was significantly improved by the addition of small amounts of LCP. This was also reflected by decreases in the steady shear viscosities, though the dynamic complex viscosities of the blends were generally similar or higher than those of the individual component polymers. Composite fibers were spun from the blends and the tensile moduli and strengths were consistent with a morphology of …
Strain Induced Crystallization Of Peek, Robert Weiss
Strain Induced Crystallization Of Peek, Robert Weiss
Robert Weiss
Strain-induced crystallization of poly(ether ether ketone) (PEEK) was studied by the use of a parallel plate rheometer. The experimental variables included preheating time, crystallization temperature, and shear rate. The crystallization kinetics were characterized by means of an induction time defined as the time elapsed from the start of shearing to the onset of crystallization. The experimental results showed that the induction time for strain-induced crystallization of PEEK was significantly shorter than that for crystallization under quiescent condition, and that strain-induced crystallization was much less temperature dependent than quiescent crystallization. The activation energy for strain-induced crystallization was found to be 0.035kcal/mole, …
Properties Of Polyethylene Modified With Phosphonate Side Groups I. Thermal And Mechanical Properties, Robert Weiss
Properties Of Polyethylene Modified With Phosphonate Side Groups I. Thermal And Mechanical Properties, Robert Weiss
Robert Weiss
Low-density polyethylene was modified by the inclusion of phosphonate ester pendent groups by using an oxidative chlorophosphonylation reaction followed by esterification of the polyethylene poly(phosphonyl chloride) with an alcohol. Two different types of phosphonate esters were prepared: dimethyl phosphonate from the reaction with methanol and a phosphonate graft copolymer from the reaction with hydroxy-terminated poly(ethylene oxide) (PEO). For the latter, oligomers with molecular weights of 350 and 750 were used. For each type of phosphonate, a series of polymers were prepared with pendent group concentrations ranging from 0 to 9.1 substituents per 100 carbon atoms. The modified polymers were characterized …
Nanoparticle-Textured Surfaces From Spin-Coating, Robert Weiss
Nanoparticle-Textured Surfaces From Spin-Coating, Robert Weiss
Robert Weiss
No abstract provided.
Molecular Dynamics Simulation Of Chain Collapse Of Random Ionomers In A Poor Solvent, Robert Weiss, Rue Xie
Molecular Dynamics Simulation Of Chain Collapse Of Random Ionomers In A Poor Solvent, Robert Weiss, Rue Xie
Robert Weiss
Chain collapse and ionic aggregation of sodium salts of lightly sulphonated polystyrene (Na-SPS) in a poor solvent were simulated by molecular dynamics of a single ionomer chain in vacuum. Ionomers with a sulphonation level from 0 to 28 mol% and a polymerisation index of 50 were constructed by virtual copolymerisation of the ionic and nonionic species. Chain collapse occurred by a three-stage process. Local collapse of the ionomer occurred in the first stage, which was marked by sharp decreases in both the radius of gyration (Rg) and the chain end-to-end distance (D). The second stage was a transition to a …
Strength Improvement Of Short Graphite Fiber-Reinforced Polypropylene, Robert Weiss
Strength Improvement Of Short Graphite Fiber-Reinforced Polypropylene, Robert Weiss
Robert Weiss
The Improvement of the tensile strength of discontinuous graphite fiber-reinforced polypropylene is described. Two methods were employed: (1) modification of the polymer backbone by the introduction of acrylic acid grafts and (2) varying the chemistry of the fiber sizing. The strength improvements attained are attributed to intermolecular interactions, such as hydrogen bonding, which improve the adhesion between the fiber and the polymer.
Compatibilization Of Blends Containing Thermotropic Liquid Crystalline Polymers With Sulfonate Ionomers, Robert Weiss
Compatibilization Of Blends Containing Thermotropic Liquid Crystalline Polymers With Sulfonate Ionomers, Robert Weiss
Robert Weiss
Zinc salts of lightly sulfonated polystyrene ionomers (Zn-SPSs) are shown to be effective compatibilizers for blends of a wholly aromatic liquid crystalline polyester (LCP) with nylon 66 (PA66) and polycarbonate (PC). Zn-SPS is miscible with PC, PA66 and the LCP, though the origins of miscibility are different for the three binary blends. Zn-SPS and PA66 mix because of strong intermolecular attractive interactions between the sulfonate and amide groups, while the ionomer is miscible with PC and the LCP as a result of intramolecular repulsive interactions along the ionomer molecules. The addition of Zn-SPS to LCP/PA66 and LCP/PC blends reduces the …
Flow-Induced Structures Of Polybutadiene/Polyisoprene Blends, Z. J. Chen, N. G. Remediakis, M. T. Shaw, Robert Weiss
Flow-Induced Structures Of Polybutadiene/Polyisoprene Blends, Z. J. Chen, N. G. Remediakis, M. T. Shaw, Robert Weiss
Robert Weiss
No abstract provided.
The Control Of The Melt Rheology And Physical Properties Of Polystyrene By Ionic Interaction, Robert Weiss, P. K. Agarwal, R. D. Lundberg
The Control Of The Melt Rheology And Physical Properties Of Polystyrene By Ionic Interaction, Robert Weiss, P. K. Agarwal, R. D. Lundberg
Robert Weiss
No abstract provided.
Explanation Of;Dark-Streak&Light Scattering Patterns And Shear-Induced Structure Development Of Phase-Separated Polymer Blends, Robert Weiss
Explanation Of;Dark-Streak&Light Scattering Patterns And Shear-Induced Structure Development Of Phase-Separated Polymer Blends, Robert Weiss
Robert Weiss
No abstract provided.
The Influence Of Intermolecular Interactions On The Melt Rheology Of A Propylene-Acrylic Acid Copolymer And Its Salts., Robert Weiss
The Influence Of Intermolecular Interactions On The Melt Rheology Of A Propylene-Acrylic Acid Copolymer And Its Salts., Robert Weiss
Robert Weiss
Ionomers based on propylene–acrylic acid copolymer have been prepared and their rheological behavior studied. With different cations the melt viscosity at any shear rate increases as tributylamine salt < acid < zinc salt < sodium salt. Similarly, the activation energies for viscous flow follow the order polypropylene ∼ tributylamine salt < acid ∼ zinc salt < sodium salt. These results are a consequence of intermolecular interactions between salt groups for the metal acrylate derivatives and hydrogen bonding for the acid derivatives. Strong ionic interactions are absent in the tributylamine salt because of steric hindrance of the bulky amine substituents. The glass transition temperatures for these …
Compatibilization Of Polymer Blends By Complexation: 1. Spectroscopic Characterization Of Interactions In Ionomer/Polyamide Blends, Yi Feng, Asher Schmidt, Robert Weiss
Compatibilization Of Polymer Blends By Complexation: 1. Spectroscopic Characterization Of Interactions In Ionomer/Polyamide Blends, Yi Feng, Asher Schmidt, Robert Weiss
Robert Weiss
Electron paramagnetic resonance (EPR), Fourier transform infrared (FTIR), and solid-state 15N nuclear magnetic resonance (15N-NMR) spectroscopies were used to characterize the structure and relative strength of the interactions between metal sulfonate and amide groups in blends of lightly sulfonated polystyrene ionomers and an N-methylated polyamide, poly(N,N‘-dimethylethylene sebacamide), and low molecular weight model complexes. The metal sulfonate groups, which aggregate in the neat ionomer, were dispersed by the polyamide in the blend as a consequence of a complexation that involved the sulfonate cation and both the carbonyl oxygen and the amide nitrogen of the polyamide. The FTIR and 15N-NMR spectra were …
Flow-Induced Mixing Of Blends Of Poly(Ethylene-Vinyl Acetate) And Solution Chlorinated Polyethylene, I. Hindawi, J. S. Higgins, A. F. Galambos, Robert Weiss
Flow-Induced Mixing Of Blends Of Poly(Ethylene-Vinyl Acetate) And Solution Chlorinated Polyethylene, I. Hindawi, J. S. Higgins, A. F. Galambos, Robert Weiss
Robert Weiss
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Polymer Alloys, Blends And Ionomers: An Overview, Robert Weiss
Polymer Alloys, Blends And Ionomers: An Overview, Robert Weiss
Robert Weiss
This chapter provides a broad overview of the subjects of polymer blends and ionomers. Specific topics concerning polymer blends include the thermodynamics of mixing of polymer-polymer pairs, polymer interfaces, rheology, and mechanical properties. For ionomers, the chemistry, structure, rheology and solution properties are discussed.
The Synthesis Of Sulfonated Polymers By Free Radical Copolymerization. (Poly(Butadiene-Co-Sodium Styrene Sulfonate)., Robert Weiss
The Synthesis Of Sulfonated Polymers By Free Radical Copolymerization. (Poly(Butadiene-Co-Sodium Styrene Sulfonate)., Robert Weiss
Robert Weiss
The copolymerization of butadiene with sodium styrene sulfonate was studied and the copolymer products characterized. In general these copolymers contain 0.5–4 mole% of sulfonated monomer. The effects of the following reaction variables are described: emulsifier type and concentration, monomers feed ratio, chain transfer agent concentration, and reaction conversion. The products were heterogeneous with regard to composition, molecular weight, and solubility behavior. Copolymers prepared under certain conditions exhibited strong intermolecular interactions derived from associations of the ionic species as observed in other ionomers.
Improvement Of The Processability Of Poly(Ether Ketone Ketone) By The Addition Of A Liquid Crystalline Polymer, Robert Weiss
Improvement Of The Processability Of Poly(Ether Ketone Ketone) By The Addition Of A Liquid Crystalline Polymer, Robert Weiss
Robert Weiss
The addition of a thermotropic liquid crystalline, wholly aromatic copolyester, TLCP, improved the melt processability of poly(ether ketone ketone), PEKK. The tensile strength and modulus of the blends also improved with increasing TLCP, but the elongation at break decreased significantly. The blends were phase-separated, but the polymers were partially miscible as evident from shifts of the glass transition temperature (Tg) of each component towards that of the other component in the blend. Similarly, the melting points (Tm) of both components were depressed by blending. When the crystallization temperature was above Tm of the TLCP, the PEKK crystallization rate in the …
Miscible Blends Of A Thermotropic Liquid Crystalline Polymer And Sulfonated Polystyrene Ionomers, Robert Weiss, Y. Ghebremeskel, L. Charbonneau
Miscible Blends Of A Thermotropic Liquid Crystalline Polymer And Sulfonated Polystyrene Ionomers, Robert Weiss, Y. Ghebremeskel, L. Charbonneau
Robert Weiss
The miscibility of a wholly aromatic thermotropic liquid crystalline polyester (LCP), Vectra® A, with lightly sulfonated polystyrene ionomers (SPS) was assessed. Blends were prepared by melt mixing in an intensive mixer. The sulfonation level and the choice of the cation used to neutralize the ionomer influenced miscibility. Zinc salts of an SPS with 5.3 mol% sulfonation were miscible at all compositions with the LCP, but lithium salts with the same sulfonation level formed two phases, a pure LCP phase and an ionomer-rich mixed phase. Zinc salts of an ionomer with 10.8 mol% sulfonation were also miscible with the LCP when …
Electron Spin Resonance Studies Of Ionic Interactions In Sulfonated Polystyrene Manganese (Ii) Salts., Robert Weiss
Electron Spin Resonance Studies Of Ionic Interactions In Sulfonated Polystyrene Manganese (Ii) Salts., Robert Weiss
Robert Weiss
No abstract provided.
Observation Of Cluster Formation In An Ionomer, Robert Weiss
Observation Of Cluster Formation In An Ionomer, Robert Weiss
Robert Weiss
No abstract provided.
A Small Angle Neutron Scattering Study Of A Semiflexible Main-Chain Liquid Crystalline Copolyester, Robert Weiss
A Small Angle Neutron Scattering Study Of A Semiflexible Main-Chain Liquid Crystalline Copolyester, Robert Weiss
Robert Weiss
No abstract provided.
Synthesis, Properties, And Structure Of Sulfonate Ionomers, Robert Weiss
Synthesis, Properties, And Structure Of Sulfonate Ionomers, Robert Weiss
Robert Weiss
The unique mechanical and rheological properties of ionomers are sources of growing academic and industrial interest. The relationship between the complex properties that ionomers exhibit and their microstructure has been the subject of numerous studies. A greater understanding of this relationship is necessary if one wishes to manipulate the ionic interactions in order to control the properties of the polymer.
Compatibilization Of Syndiotactic Polystyrene And A Thermotropic Liquid Crystalline Polymer Blend With A Zinc Salt Of A Sulfonated Polystyrene Ionomer, Robert Weiss
Robert Weiss
A zinc salt of a lightly sulfonated (4.5 mol %) polystyrene ionomer was used to compatibilize a 3/1 (w/w) blend of syndiotactic polystyrene and a wholly aromatic thermotropic liquid-crystalline polymer (TLCP). The addition of the ionomer significantly reduced the dispersed TLCP domain size and improved the tensile strength, ultimate elongation, and flexural toughness of the blend
Microstructure Of Block Copolymers Of Polystyrene And Poly(Ethylene-Alt-Propylene), Robert Weiss
Microstructure Of Block Copolymers Of Polystyrene And Poly(Ethylene-Alt-Propylene), Robert Weiss
Robert Weiss
The microstructure and microphase behaviour of diblock (Ma ≈ 27 and 50 kg mol−1) and triblock (Ma ≈ 50kg mol−1) copolymers of polystyrene (PS) and poly(ethylene-alt-propylene) (PEP) were studied by small angle X-ray scattering (SAXS), transmission electron microscopy (TEM) and dynamic mechanical thermal analysis (DMTA). The composition was varied from 10 wt.% to 50 wt.% PS. The morphology of solution-cast and compression-moulded samples was compared. The common packing arrangements of body-centred-cubic (BCC) spheres, hexagonal-close-packed (HCP) cylinders and alternating lamellae were observed for the PS microdomains using SAXS and TEM. A microphase texture of PS spheres with a liquid-like packing (LLP) …
Analysis Of Caprolactam Polymerization, Robert Weiss
Analysis Of Caprolactam Polymerization, Robert Weiss
Robert Weiss
No abstract provided.
Characterization Of The Block Microstructure In Block Copolymer Ionomers Using Small Angle X-Ray Scattering, S. Mani, Robert Weiss, C. E. Williams, S. F. Hahn
Characterization Of The Block Microstructure In Block Copolymer Ionomers Using Small Angle X-Ray Scattering, S. Mani, Robert Weiss, C. E. Williams, S. F. Hahn
Robert Weiss
The block microstructure of a series of diblock copolymer ionomers was investigated using synchrotron small-angle x-ray scattering (SAXS). The base materials used were poly[styrene-b-(ethylene/propylene)] (SEP) diblock copolymers with a constant total molecular weight of ca. 50 kg/mol, but three different compositions : 20.3 wt%, 35.6 wt% and 50.4 wt% polystyrene (PS). The polystyrene microphase structures for these unmodified diblock copolymers were cylindrical, lamellar and lamellar, respectively. Ionomers were synthesized from the block copolymers by lightly sulfonating the PS blocks, followed by neutralization to the sodium and zinc salts. The introduction of ionic species into the PS blocks perturbed the block …
The Development Of The Ionic Microphase In Sulfonated Poly(Ethylene-Co-Propylene-Co-Ethylidene Norbornene) Ionomers During Physical Aging, Robert Weiss
Robert Weiss
No abstract provided.