Competition from Metal

Metal replacement has been a main driver for the use of polyamide in automotive applications in the past. Most of the obvious replacement of metal by PA has already taken place in the car interior, exterior and electrical systems areas. Under-the-bonnet applications however still offer some scope for further penetration by polyamide, particularly for high-performance grades. 

Polyamide for instance has been replacing metal in manufacture of the air inlet manifold for a number of years. Industry estimates are for PA to achieve market penetration in Europe of 85% by 2005. Levels in NAFTA and Japan are expected to be somewhat lower, but growth rates there somewhat higher. Global production of inlet manifolds made of polyamide reached 18 million in 2001. 

Metal may, however, come back to threaten plastic because of the trend towards high-powered small volume engines which generate a lot of heat per unit volume, and from higher emission standards. 

There is some re-substitution taking place with plastics being replaced by steel for some under-the-bonnet parts. Steel-makers are improving their products to make thinner and lighter steel sheet with even higher tensile strength steel. 

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The Ultem PEI resins compete with PAI, polyarylethersulfone, nylon, and polyester resins in certain markets. General Electric Co. is the sole U.S. manufacturer of PEI resins. High cost coupled with stiff competition from metals and ceramics have limited growth. 

The chief advantage of wood for containers is that many common species are free from harmful contaminants. For this reason wood had widespread use in the food and beverage industries, but it has now suffered severe competition from corrosion-resistant metals, plastics and paper products. Oak had a very extensive use in tight cooperage in the brewing industry, and its use for barrels still survives in the maturing of whisky and brandy and in the wine industries. Wood is particularly useful where acetic acid is present as this acid is corrosive to most common metals. 

Water birds have not been shown to be directly affected by acidification. However, the prey of waterbirds may be of concern as these lower food-chain organisms may have elevated levels of toxic metals related to acidification of their habitat. Moreover, most water birds rely on some component of the aquatic food-chain for their high protein diet. Invertebrates that normally supply caJcium to egg-laying birds or their growing chicks are among the first to disappear as lakes acidify. As these food sources are reduced or eliminated due to acidification, bird habitat is reduced and reproductive rate of the birds is affected. The Common Loon is able to raise fewer chicks, or none at all, on acidic lakes where fish populations are reduced 37 and 5S). However, in some isolated cases, food supplies can be increased when competitive species are eliminated (e.g.. Common Goldeneye ducks can better exploit insects as food when competition from fish is eliminated). The collective influences of acidification are difficult to quantify on a specific area basis but for species that rely on a healthy aquatic ecosystem to breed, acidification remains a continuing threat in thousands of lakes across eastern North America 14). 

Alternative paths for decomposition of the metal carboxylate can lead to ketones, acid anhydrides, esters, acid fluorides (1,11,22,68,77,78), and various coupling products (21,77,78), and aspects of these reactions have been reviewed (1,11). Competition from these routes is often substantial when thermal decomposition is carried out in the absence of a solvent (Section III,D), and their formation is attributable to homolytic pathways (11,21,77,78). Other alternative paths are reductive elimination rather than metal-carbon bond formation [Eq. (36)] (Section III,B) and formation of metal-oxygen rather than metal-carbon bonded compounds [e.g., Eqs. (107) (119) and (108) (120). Reactions (36) and (108) are reversible, and C02 activation (116) is involved in the reverse reactions (48,120). 

Diazomethane is also decomposed by N O)40 -43 and Pd(0) complexes43 . Electron-poor alkenes such as methyl acrylate are cyclopropanated efficiently with Ni(0) catalysts, whereas with Pd(0) yields were much lower (Scheme 1)43). Cyclopropanes derived from styrene, cyclohexene or 1-hexene were formed only in trace yields. In the uncatalyzed reaction between diazomethane and methyl acrylate, methyl 2-pyrazoline-3-carboxylate and methyl crotonate are formed competitively, but the yield of the latter can be largely reduced by adding an appropriate amount of catalyst. It has been verified that cyclopropane formation does not result from metal-catalyzed ring contraction of the 2-pyrazoline, Instead, a nickel(0)-carbene complex is assumed to be involved in the direct cyclopropanation of the olefin. The preference of such an intermediate for an electron-poor alkene is in agreement with the view that nickel carbenoids are nucleophilic 44). 

The disadvantages of organic dyes (low photostability, insufficient brightness, short lifetimes, etc.) have resulted in competition from luminescent metal-ligand complexes, semiconductor nanoparticles (Quantum Dots), and conjugated polymers. These new materials show advanced performance in a variety of applications... 

Note that it is important to avoid carboxy cation exchangers. A proportion of the charged groups on a carboxy cation exchanger exist in a relative proximity that endows them with the ability to chelate metal ions. These chelating sites may competitively displace metals from proteins in the sample, creating a source of assay variability. Use a noncarboxy cation exchanger such as sulfomethyl, ethyl, or propyl. 

Relaxivities were measured either as a function of the applied field or in titration experiments at 20 MHz in anhydrous acetonitrile solutions of Gd(C104)3, i.e., in the simplest possible conditions with no competition from water or coordinating anions for the complexation of the metal ions. 

Smelter Acid. If acid is produced involuntarily, as in a smelter operation, it is possible to estimate the cost of acid production in the same manner as that for an elemental sulfur acid plant. To the smelter, however, acid output is simply a mandated concomitant of the process required to produce the metal. Depending on the location of the smelter, the sources of demand, the size of the market, and competition from other producers, the acid sale price may or may not be sufficiently high even to yield a positive net-back, much less a desired rate of return on investment for the acid portion of the operation. This situation does not necessarily lead to closure. Positive or negative, the effect should be registered only in the overall profitability of the entire smelter operation. 

The pH of the medium always has a strong effect on metal binding. Competition with protons means that metal complexes tend to be of weak stability at low pH. Anions of carboxylic acids are completely protonated below a pH of 4 and a metal can combine only by displacing a proton. However, at pH 7 or higher, there is no competition from protons. On the other hand, in the case of ethylenediamine, whose pKa values are 10.2 and 7.5 (Table 6-9), protons are very strong competitors at pH 7, even with a strongly com- c... 

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