An analysis has been made of the literature on tribology of polymer nanocomposites prepared by compounding nanofillers with molten thermoplastics. A process is described for preparing nanocomposites with various polymer binders by reactive extrusion. The introduction of nanofillers (carbon nanomaterials, layered clays, metals, and metal-containing compounds) into thermoplastics influences the kinetics and mechanism of tribochemical transformations in a friction contact with metals or other materials. Nanofillers affect significantly the physicochemical behavior of macromolecules, as well as the macromolecular transformations, under the conditions of frictional interaction. This can be explained by adsorption (chemisorption) of functional groups found on the particle surface, variations in polymer crystallinity and morphology, constrained molecular (segmental) mobility in macrochains, and catalytic (inhibiting) effects of the additives on the course of contact reactions. As a consequence, alterations occur...

Polymer Nanocomposites with Thermoplastic Matrices—Processing and Tribology

An analysis has been made of the literature on friction and wear of polymer nanocomposites prepared by compounding nanofillers with molten thermoplastics. A process is described for preparing the nanocomposites with various binders, for example, polar and nonpolar thermoplastics, aliphatic, aromatic, and partially aromatic polymers, as well as amorphous and partially crystalline polymers by reactive extrusion. The most important group of triboengineering nanocomposites includes thermoplastics containing the following fillers, carbon nanomaterials, layered clays, metals, and metal-containing compounds. The introduction of nanofillers into thermoplastics influences the kinetics and mechanism of tribochemical transformations in a friction contact with metals or other materials. Nanofillers significantly affect the physicochemical behavior of macromolecules, as well as the macromolecular transformations, at the conditions of frictional interaction. This can be explained by adsorption (chemisorption) of functional groups found on the particle surface, variations in polymer crystallinity and morphology, constrained molecular (segmental) mobility in macrochains, and catalytic (inhibiting) effects of the additives on the course of contact reactions. As a consequence, alterations occur in the formation of transfer layers and wear debris, along with the parameters of friction. Depending on the polymer, the nature and concentration of the fillers, the latter can either improve or impair the performance parameters of friction pairs.

Tribological behavior of polymer nanocomposites produced by dispersion of nanofillers in molten thermoplastics

CHAPTER 5 - Tribological behavior of polymer nanocomposites produced by dispersion of nanofillers in molten thermoplastics

Thermoplastic molding composition comprises (a) 10-99.85 wt.% a thermoplastic polymer or a combination of different thermoplastic polymers, (b) 0.05-10 wt.% at least one salt of metal cations and thermally activatable reducing anions, preferably non-formate anions, which enter into a reaction at 100-450[deg] C and with a standard potential of less than 0 V at 25[deg] C, with respect to standard hydrogen electrode, with sufficient reaction rate, which represents reaction of at least 10 mole% the thermally activatable anion for one hour, and (c) 0.1-70 wt.% further ingredients. Independent claims are also included for: (1) fibers, films or moldings, which are obtained by injection molding, extruding or blow molding of the above thermoplastic molding composition; (2) producing the thermoplastic molding composition, comprising mixing the components (a)-(c) at a temperature of 220-400[deg] C, preferably by blending, kneading, compounding, extruding or rolling; and (3) reducing photo- and/or thermo-oxidative degradation of the thermoplastic polymers, or films, fibers or moldings produced from the thermoplastic polymers, comprising providing the salt of the metal cations and the thermally activatable reducing anions, preferably non-formate anions, and adding the thermoplastic polymer to it.

Thermoplastic moulding compositions

Electrochemically active nanocrystalline tungsten oxide was synthesized in supercritical carbon dioxide from tungsten hexacarbonyl at 150 °C and 400 bar in the presence of oxygen (partial pressure of 15 bar). The supercritical fluid is a solvent for the precursor (i.e., this is a sc solvothermal synthesis route), whereas the admixed gaseous oxygen serves as an oxidizer, promoting thermal decomposition of the precursor. During the substrate-free synthesis, 200–500 nm aggregates are formed. They consist of smaller grains having the size of about 100 nm. Therefore, a certain structural hierarchy is detected. The electrochemical activity of the as-synthesized particulate material is pronouncedly increasing during both potential cycling and exposure in an aqueous aerated electrolyte. After such a hydration/oxidation process, the electrochemical response of the material shows rather fast and reversible recharging of the entire tungsten-containing phase. This is an indication of facilitated proton transport in bulk of the tungsten oxide phase synthesized in the supercritical carbon dioxide with subsequent hydration/oxidation. Quite differently, the material synthesized at the same temperature only in compressed oxygen (partial pressure of 15 bar) without any presence of supercritical carbon dioxide is highly crystalline one. It does not demonstrate any significant electrochemical rechargeability; neither is the response improving with hydration/oxidation.

Electrochemically active dispersed tungsten oxides obtained from tungsten hexacarbonyl in supercritical carbon dioxide

Composites prepared at 200°C by the melt compounding of copolymer polyamide 6/66 and ferric chloride, ferric oxalate, cupric chloride, cupric formiate, cupric acetate, Cr-carbonyl, Mo-carbonyl, or W-carbonyl have been studied. The solution stability and aggregation suppression for nanoparticles in a polyamide can be explained by the formation of stable polymer–metal complexes. The nitrogen atoms of amide and amine groups of polymers serve as ligands for the coordination compounds that form. The dynamic viscosity of the solutions suggests that Cr-carbonyl forms mostly intermolecular complexes, whereas ferric oxalate, ferric chloride, cupric formiate, cupric acetate, cupric chloride, Cr-carbonyl, Mo-carbonyl, and W-carbonyl form intramolecular complexes. The critical concentrations for metal-containing compounds at which a dispersion rises to nanodimensions without aggregating in the polymer matrix under the experimental conditions are 0.024 wt % for ferric oxalate, 0.12 wt % for ferric chloride, 0.08 wt % for cupric formiate, 0.096 wt % for cupric acetate, and 0.19 wt % for cupric chloride. Metal carbonyls undergo dispersion (with their concentration up to 5 wt %) in polyamide 6/66 without aggregating into larger formations. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007

Metal–polymer nanocomposites produced by the melt‐compounding interaction of an aliphatic polyamide with metal particles

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Metal–polymer nanocomposites produced by the melt‐compounding interaction of an aliphatic polyamide with metal particles