Oxidation impact

Catalytic forms of copper, mercury and silver acetylides, supported on alumina, carbon or silica and used for polymerisation of alkanes, are relatively stable [3], In contact with acetylene, silver and mercury salts will also give explosive acetylides, the mercury derivatives being complex [4], Many of the metal acetylides react violently with oxidants. Impact sensitivities of the dry copper derivatives of acetylene, buten-3-yne and l,3-hexadien-5-yne were determined as 2.4, 2.4 and 4.0 kg m, respectively. The copper derivative of a polyacetylene mixture generated by low-temperature polymerisation of acetylene detonated under 1.2 kg m impact. Sensitivities were much lower for the moist compounds [5], Explosive copper and silver derivatives give non-explosive complexes with trimethyl-, tributyl- or triphenyl-phosphine [6], Formation of silver acetylide on silver-containing solders needs higher acetylene and ammonia concentrations than for formation of copper acetylide. Acetylides are always formed on brass and copper or on silver-containing solders in an atmosphere of acetylene derived from calcium carbide (and which contains traces of phosphine). Silver acetylide is a more efficient explosion initiator than copper acetylide [7],... 

Czuryszkiewicz T, Rosenholm J, Kleitz F, Linden M (2002) Synthesis and characterization of mesoscopically ordered surfactant/cosurfactant templated metal oxides. Impact of Zeolites and Other Porous Materials on the New Technologies at the Beginning of the New Millennium, Book Series Studies in Surface Science and Catalysis, Pts A and B 142 1117-1124... 

To see how high-fe oxides impact the transistor performance, one can look at the equation for the drain current of an MOS transistor [11] ... 

Materials/characteristics Heat stabilizers/anti-oxidants impact modiliers pigments, fillers, reinforcements... 

Tuller HL (1997) Semiconduction and mixed ionic-electronic conduction in nonstoichiometric oxides impact and control. Solid State Ionics 94 63-74... 

The solid solution formed with iron oxides impacts the reduction rate, for example, addition of 1%-10% CaO increases the reducibility, with the product of the reduction of CaO and a-Fe sponge. CaO and magnetite form CaxFe3 x04, which affects both the thermodjmamics and kinetics together, and Ca2Fe205 has the lowest rate of reduction (Fig. 5.21). ... 

ADDITIVES TO IMPROVE THE POLYMER CHARACTERISTICS The polymer characteristics like resin s stability to oxidation, impact resistance, hardness, surface tension, flame resistance, and so on can be improved by incorporating some additives with the resin during film manufacture. Additives can also facilitate extmsion and molding, controls blocking and reduces cost. 

J.P. Bolanos, M. Delgado-Esteban, A. Herrero-Mendez, S. Femandez-Femandez, A. Almeida, Regulation of glycolysis and pentose-phosphate pathway by nitric oxide impact on neuronal survival., Biochim. Biophys. Acta 1777 (2008) 789-793. 

Fig. 8.14 (a) Oxidative impact spikes for silver nanoparticles in authentic seawater media, (b) Size distribution for silver nanoparticles in seawater obtained via APC expressed as the number of atoms (Ai) per impacting nanoparticle and deconvoluted to reveal contributions from aggregates. Reproduced (a) and adapted (b) by permission of The Royal Society of Chemistry... 

In addition to particle identification and sizing, the impact method can also be used to measure the concentration of nanoparticles in solution. This is best done by measuring oxidative impacts at a micro-disc electrode, typically made of carbon. The current (I)-time transient at such an electrode following the application of a potential sufficient to oxidise species under diffusion control in an n-electron process is... 

Thermal Oxidative Stability. ABS undergoes autoxidation and the kinetic features of the oxygen consumption reaction are consistent with an autocatalytic free-radical chain mechanism. Comparisons of the rate of oxidation of ABS with that of polybutadiene and styrene—acrylonitrile copolymer indicate that the polybutadiene component is significantly more sensitive to oxidation than the thermoplastic component (31—33). Oxidation of polybutadiene under these conditions results in embrittlement of the mbber because of cross-linking such embrittlement of the elastomer in ABS results in the loss of impact resistance. Studies have also indicated that oxidation causes detachment of the grafted styrene—acrylonitrile copolymer from the elastomer which contributes to impact deterioration (34). 

Examination of oven-aged samples has demonstrated that substantial degradation is limited to the outer surface (34), ie, the oxidation process is diffusion limited. Consistent with this conclusion is the observation that oxidation rates are dependent on sample thickness (32). Impact property measurements by high speed puncture tests have shown that the critical thickness of the degraded layer at which surface fracture changes from ductile to brittle is about 0.2 mm. Removal of the degraded layer restores ductiHty (34). Effects of embrittled surface thickness on impact have been studied using ABS coated with styrene—acrylonitrile copolymer (35). 

Analysis of Trace or Minor Components. Minor or trace components may have a significant impact on quaHty of fats and oils (94). Metals, for example, can cataly2e the oxidative degradation of unsaturated oils which results in off-flavors, odors, and polymeri2ation. A large number of techniques such as wet chemical analysis, atomic absorption, atomic emission, and polarography are available for analysis of metals. Heavy metals, iron, copper, nickel, and chromium are elements that have received the most attention. Phosphoms may also be detectable and is a measure of phosphoHpids and phosphoms-containing acids or salts. 

TetrabromobisphenoIA. Tetrabromobisphenol A [79-94-7] (TBBPA) is the largest volume bromiaated flame retardant. TBBPA is prepared by bromination of bisphenol A under a variety of conditions. When the bromination is carried out ia methanol, methyl bromide [74-80-9] is produced as a coproduct (37). If hydrogen peroxide is used to oxidize the hydrogen bromide [10035-10-6] HBr, produced back to bromine, methyl bromide is not coproduced (38). TBBPA is used both as an additive and as a reactive flame retardant. It is used as an additive primarily ia ABS systems, la ABS, TBBPA is probably the largest volume flame retardant used, and because of its relatively low cost is the most cost-effective flame retardant. In ABS it provides high flow and good impact properties. These benefits come at the expense of distortion temperature under load (DTUL) (39). DTUL is a measure of the use temperature of a polymer. TBBPA is more uv stable than decabrom and uv stable ABS resias based oa TBBPA are produced commercially. 

Triphenyl phosphate [115-86-6] C gH O P, is a colorless soHd, mp 48—49°C, usually produced in the form of flakes or shipped in heated vessels as a hquid. An early appHcation was as a flame retardant for cellulose acetate safety film. It is also used in cellulose nitrate, various coatings, triacetate film and sheet, and rigid urethane foam. It has been used as a flame-retardant additive for engineering thermoplastics such as polyphenylene oxide—high impact polystyrene and ABS—polycarbonate blends. 

Phosphonium Salt—Urea Precondensate. A combination approach for producing flame-retardant cotton-synthetic blends has been developed based on the use of a phosphonium salt—urea precondensate (145). The precondensate is appUed to the blend fabric from aqueous solution. The fabric is dried, cured with ammonia gas, and then oxidized. This forms a flame-resistant polymer on and in the cotton fibers of the component. The synthetic component is then treated with either a cycUc phosphonate ester such as Antiblaze 19/ 19T, or hexabromocyclododecane. The result is a blended textile with good flame resistance. Another patent has appeared in which various modifications of the original process have been claimed (146). Although a few finishers have begun to use this process on blended textiles, it is too early to judge its impact on the industry. 

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