Materials Literature
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Reactor powder of a number of commercial ultra-high molecular weight polyethylenes synthesized on heterogeneous Ziegler–Natta catalyst in a conventional slurry process have been investigated with the help of scanning electron microscopy (SEM), wide-angle x-ray scattering (WAXS), differential scanning calorimetry (DSC)…
The kinetic model proposed by Chen and Wu (Chen, S.A.; Wu, K.C. Kinetics of polyesterification. II. Foreign acid-catalyzed dibasic acid and glycol systems. J. Polym. Sci. 1982, 20, 1819–1831.) for the formation of unsaturated polyester resins by reaction between diols and anhydrides has been modified to take into acco…
Micromold with microchannels was employed in assembly of directional free-standing single-walled carbon nanotube (SWNT) strings at room temperature. The new postgrowth assembly approach could, in principle, apply not only to a wide range of SWNTs in their soluble or dispersible forms, including small diameter (0.7-0.8…
Many normally ductile semi-crystalline polymers, such as polyamide-6 (or 6,6) (Nylon), high density polyethylene (HDPE), and isotactic polypropylene (iPP) are known to be brittle under impact loading. Some general principles for improvement of toughness of semi-crystalline polymers that rely on the reduction of plasti…
Polyanilines (PANI) were synthesized from peroxidase-catalyzed polymerization of aniline with and without the presence of a template in the aqueous buffer solution of pH 4.3. The template used was poly(vinylphosphonic acid) (PVP). Solid-state 13C and 15N CP/MAS NMR techniques were applied to characterize the structure…
The influence of cooling rate from the melt on the polymorphism and crystallinity is investigated as a function of isotacticity and stereo-defect distribution in polypropylenes. Detailed analysis of wide angle x-ray diffraction patterns shows that crystallinity in the materials used is nearly independent of the experi…
Thermoplastic elastomers have been prepared by blending polypropylene (PP), natural rubber (NR), and recycle rubber powder (RRP). The blends were melt-mixed using a Brabender Plasticorder torque rheometer at 190°C and 50 rpm. A fixed 70:30 blend ratio (wt%) of PP and rubber was prepared. The effect of partial replacem…
Analysis of correlations between various physical properties of solids provides a formulation of simple criteria applicable to the search for new superhard materials. The prospects for the synthesis of new substances with the key elastic moduli, whose values approach or even exceed those of diamond are also discussed.…
The condensation copolymerization of Dimethyl 5-hydroxyisophthalate (1) with Polyethylene glycols (PEGs) (2a–2d) of varying molecular weights, catalyzed by Novozyme-435 (immobilized Candida antarctica lipase B) in bulk is reported. The structures of the resulting polymers, Poly[(poly(oxyethylene)-oxy-5-hydroxyisophtha…
Reinforced thermoplastics generally are produced by incorporation of reinforcement agents or fillers into thermoplastic resins. The utilization of lignocellulosic material as filler with reinforcement in polymer matrix has received much interest due to its lower price and other properties. A composite of polystyrene r…
Crystallization and melting behavior of β-nucleated propylene/1-pentene random copolymers were studied. Samples with different comonomer content were nucleated with the calcium salt of suberic acid. The WAXS, differential scanning calorimetry (DSC), and polarized light microscopy (PLM) measurements showed that morphol…
This article is an overview of our investigations of polymorphism in isotactic polypropylene. We suggest the reason for the formation of different forms is perturbations in the mobility of the chains during crystallization. In this work, we try to prove this hypothesis considering the influence of the presence of smal…
The molecular weight (MW) dependence of the linear crystal growth rate (G) and the influence of the supercooling on the relationship between MW and G at a given supercooling were studied for poly(ethylene succinate). The spherulite growth rate was measured over a wide range of temperature. It had a bell-shape with a m…
Several aspects of the structure, morphology, growth transitions, and optical properties of isotactic polypropylene (iPP) are considered; we deal mostly with its two more classical α and β crystal modifications (αiPP and βiPP). A derivation of the frustrated crystal structure of βiPP is presented. The existence of two…
The application properties of plastic products are significantly influenced by the structural changes after conversion, resulting from a combination of post-crystallization and physical aging for semicrystalline materials. For three different types of polypropylene—homopolymer, ethylene/propylene random- and heteropha…
The microstructure of a metal-centered six-arm star block copolymer, amphiphilic iron tris(bipyridine)-centered poly(2-ethyl-2-oxazoline)- b -poly(2-undecyl-2-oxazoline), [Fe{bpy(PEOX−PUOX) 2 } 3 ] 2+, was investigated with small-angle X-ray scattering (SAXS), wide-angle X-ray scattering (WAXS), transmission electron…
Electrospinning is a simple technique to form high surface area membranes using large static electric potentials. An application, taking advantage of such a high surface area, is a dye-sensitized photovoltaic cell, wherein a chromophore molecule absorbs light before being oxidized to generate a photocurrent. We report…
The synthesis, characterization, and biolocalization properties of new, fully water-soluble sapphyrins is reported. These systems, which display light absorbing features that make them of potential interest as photodynamic therapy (PDT) sensitizers, were found to localize selectively in pancreatic carcinoma tissue in…
Spectroscopy coupled with density functional calculations has been used to define the spin state, oxidation states, spin distribution, and ground state wave function of the mu4-sulfide bridged tetranuclear CuZ cluster of nitrous oxide reductase. Initial insight into the electronic contribution to N2O reduction is deve…
Single-crystal particles of mesoporous niobium−tantalum mixed oxide with a wormhole-like structure were successfully prepared and characterized. The mixed oxide was prepared by a neutral templating method, and the samples provided have thick walls and an unordered pore structure. Neutral block copolymer, HO(CH 2 CH 2…