Ageing superior

Long-chain esters of pentaerythritol have been used as pour-point depressants for lubricant products, ranging from fuel oils or diesel fuels to the high performance lubricating oils requited for demanding outiets such as aviation, power turbines, and automobiles. These materials requite superior temperature, viscosity, and aging resistance, and must be compatible with the wide variety of metallic surfaces commonly used in the outiets (79—81). 

EPDM is a terpolymer of ethylene, propylene, and a small amount (<10%) of an unsaturated diene third monomer to provide a cure site. Unlike the elastomers previously discussed, the unsaturation in EPDM is not in the main chain, but it is pendent to the chain. Peroxide cure gives superior aging resistance and low compression set. 

Most flexible foams produced are based on polyether polyols ca 8—10% (15—20% in Europe) of the total production is based on polyester polyols. Elexible polyether foams have excellent cushioning properties, are flexible over a wide range of temperatures, and can resist fatigue, aging, chemicals, and mold growth. Polyester-based foams are superior in resistance to dry cleaning and can be flame-bonded to textiles. 

Asphalt (bitumen) also occurs in various oil sand (also called tar sand) deposits which occur widely scattered through the world (17) and the bitumen is available by means of various extraction technologies. A review of the properties and character of the bitumen (18) suggests that, when used as an asphaltic binder, the bitumen compares favorably with specification-grade petroleum asphalts and may have superior aging characteristics and produce more water-resistant paving mixtures than the typical petroleum asphalts. 

Some of the terpolymers containing high levels of AGE give superior sour gasoline and ozone resistance, particularly dynamic ozone resistance. Since the unsaturation is not in the polymer backbone, it can be, and apparentiy is, sacrificed under sour gasoline or ozone aging. This protection scheme is limited with the peroxide and sulfur cure systems as they involve the aHyl functionaUty of the polymer. The protection is maximized when a dinucleophilic curative, such as trithiocyanurate, is used. 

The commercial success of ABS polymers has led to the investigation of many other polyblend materials. In some cases properties are exhibited which are superior to those of ABS and some of the materials are commercially available. For example, the opacity of ABS has led to the development of blends in which the glassy phase is modified to give transparent polymers whilst the limited light aging has been countered by the use of rubbers other than polybutadiene. 

Heat aging resistance does not appear to be as good as with the bis-phenol A epoxide but outdoor weathering is said to be superior. 

PPG would allow more metal at the expense of the oxidizer to further energize the composition. In addition, HTPB is frequently preferred over PPG because of its superior mechanical properties, better aging characteristics, and lower glass-transition temperature (Tg). The latter is especially desirable because at low temperature, the higher strain rates produced by motor ignition decrease the elongation of the composite rather markedly. 

A recent study compared 144 patients treated within 6 hours of symptom onset with I AT using urokinase versus 147 patients treated with aspirin who were matched for age and stroke severity according to National Institutes of Health Stroke Scale (NIHSS) (median 14). The study demonstrated superiority of LAT to aspirin in patients achieving an mRS score of 0-2 (56% vs. 42%, p = 0.037) and in patients achieving an mRS score of 0-1 at 2 years (40% vs. 24%, p = 0.008) with no difference in mortality (23% vs. 24%). °... 

A PPI may be warranted in patients older than 60 years of age.29 Proton pump inhibitors are the most useful option because they have superior efficacy and are dosed once daily. Elderly patients maybe sensitive to the central nervous system effects of metoclopramide and H2RAs. 

Copper was used in Europe from about 2000 till 1800 BC (Copper Age). Thereafter bronze was used the alloy with about 20 % tin has superior properties. 

In the nineteenth century dammar, a soft resin derived from trees of southern Asia was introduced in Europe and used for making colourless varnish. Mixed with oil of turpentine it has become the preferred varnish for oil painting, due to its superior optical properties and better ageing stability than the other natural resins. 

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