Key properties

The Hamaker constant can be evaluated accurately using tire continuum tlieory, developed by Lifshitz and coworkers [40]. A key property in tliis tlieory is tire frequency dependence of tire dielectric pennittivity, (cij). If tills spectmm were tlie same for particles and solvent, then A = 0. Since tlie refractive index n is also related to f (to), tlie van der Waals forces tend to be very weak when tlie particles and solvent have similar refractive indices. A few examples of values for A for interactions across vacuum and across water, obtained using tlie continuum tlieory, are given in table C2.6.3. 

Key properties of alkyds are dimensional stability, colorability, and arc track resistance. Chemical resistance is generally poor. 

Key properties of cellulose nitrate are good dimensional stability, low water absorption, and toughness. Its disadvantages are its flammability and lack of stability to heat and sunlight. 

Key properties are its flexibility, translucency, and resistance to all known chemicals except molten alkali metals, elemental fluorine and fluorine precursors at elevated temperatures, and concentrated perchloric acid. It withstands temperatures from —270° to 250°C and may be sterilized repeatedly by all known chemical and thermal methods. 

Its key properties are its excellent transparency, rigidity, and chemical resistance, plus its resistance to impact and to high temperatures. It withstands repeated autoclaving, even at 150°C. 

Its key properties are good resistance to oils and a very low permeability to most gases. 

Poly(vinyl chloride) as previously discussed in Sec. 10.3, Formulas and Key Properties of Plastic Materials, has the following structures ... 

An extensive new Section 10 is devoted to polymers, rubbers, fats, oils, and waxes. A discussion of polymers and rubbers is followed by the formulas and key properties of plastic materials. Eor each member and type of the plastic families there is a tabulation of their physical, electrical, mechanical, and thermal properties and characteristics. A similar treatment is accorded the various types of rubber materials. Chemical resistance and gas permeability constants are also given for rubbers and plastics. The section concludes with various constants of fats, oils, and waxes. 

Catalyst performance depends on composition, the method of preparation, support, and calcination conditions. Other key properties include, in addition to chemical performance requkements, surface area, porosity, density, pore size distribution, hardness, strength, and resistance to mechanical attrition. 

Improved Com fort Properties. Wear comfort generally means cotton-like properties. The abiUty to absorb moisture from the skin and the softness of cotton fabrics are considered to be the two key properties for comfort. The extremely fine denier of cotton fibers accounts for its softness. 

Drugs. Ttifluoromethyl-based pharmaceuticals had been limited to phenothiatine tranquilizers and benzothiadiazine 1,1-dioxide diuretics (qv). However, new dmgs have been developed (Table 11). One of the key properties of the CF group is its high lipophilicity it increases the Hpid solubiUty of the pharmaceutical and thus accelerates absorption and transport within the host organism. 

The light weight of these products reduces user s shipping costs and conserves energy in transportation. These products are reusable, a key property from economic, ecological, and energy conservation standpoints. Most products are available in bulk densities of 4.0 to 4.8 kg/m (0.25 to 0.30 lb/fT). Average price is about 1.50 per pound from the manufacturer. 

The four key properties of inks are drying, rheology, color, and end use properties. Use properties are those considerations that determine how printed substrates function throughout all processing and usage from the time of printing throughout the useflil life of the printed product. 

Color and Coloring Materials. The third key property of all types of ink is color which may very weU be the most important one to the consumer because it has such a great psychological impact. Color (qv) has three different attributes described as hue or shade, saturation or chroma, and lightness or value. 

Low temperature formabiHty and resiHence are key properties in the area of shoe components, ie, box toes and counters. These ionomer components are not seen by the purchaser of the finished article, but provide comfort and durabiHty in high quaHty footwear. 

Hydrolysis and Polycondensation. One of the key properties of polyamides relates to the chemical equihbrium set up when the material is polymerized. The polymerization of nylon is a reversible process and the material can either hydrolyze or polymerize further, depending on the conditions. 

Tables 5 and 6 summarize key properties and appHcations for miscible and immiscible blends which are either commercial as of 1996 or were commercialized in the past (2,314—316,342,343). Most of the Hsted blends contain only two primary components, although many are compatibiLized and impact-modified. Consequently, an immiscible system consisting of two primary components or phases may contain impact modifiers for each phase and a compatihilizer copolymer, for a total of five or more components.

Monohydroxyaluminum distearate, (HO)Al(OOC(CH2) gCH2)2, used to be the largest selling aluminum carboxylate (1). Although stiU sold, the product is no longer Hsted in the U.S. International Trade Commission Report (1) because of low volume or confidentiahty constraints because of too few supphers. Aluminum distearate is a white powder that is insoluble in water, alcohol, and ether. A key property is its abiUty to gel vegetable oils and hydrocarbons. Aluminum distearate is prepared by the reaction of aqueous sodium stearate with aqueous aluminum sulfate or chloride at pH 7.3. Aluminum monostearate is formed if the sodium stearate solution is held at pH 9.5 (44). 

Typical substrates for siUcone release coatings are supercalendered kraft paper, glassines, and thermally sensitive films such as polyethylene and polypropylene. Ideal curing conditions are 150°C or lower, and line speeds are as fast as 460 m /min. Key properties for release coatings are cure speed, integrity of cure, and stable release values. 

A key property associated with chlorinated paraffins, particularly the high chlorine grades, is nonflammability, which has led to their use as fire-retardant additives and plasticizers in a wide range of polymeric materials. The fire-retardant properties are considerably enhanced by the inclusion of antimony trioxide. 

Equation 2 defines the basic mode of operation of the dryer. The heat-transfer coefficient is a key property of the dryer configuration. 

Not every polymer can be manufactured successfully into a contact lens. Several important properties for both ocular physiology and patient handling are required of a material for a contact lens appHcation (1,11). In addition, the type of lens appHcation, ie, rigid, flexible, or soft, will dictate the range and importance of the key properties. 

Water Content and Refractive Index. The water content of a hydrophilic contact lens is a determinant of other properties. The relationship of water content and Dk is discussed above. Water content in lenses is inversely related to refractive index (23), a key property for vision correction. A lens material with a higher refractive index refracts light to a greater degree, allowing more vision correction with a thinner material. The water content of a lens is generally determined gravimetricaHy or inferred from the relationship to refractive index, measured with a refractometer (24). 

Although a variety of test methods, eg, Dk, modulus, and tear strength, exist to determine key properties of potential contact lens materials, a number of properties, eg, wettabihty and deposition, have no predictive methodology short of actual clinical experience. 

When simple Hquids like naphtha are cracked, it may be possible to determine the feed components by gas chromatography combined with mass spectrometry (gc/ms) (30). However, when gas oil is cracked, complete analysis of the feed may not be possible. Therefore, some simple definitions are used to characterize the feed. When available, paraffins, olefins, naphthenes, and aromatics (PONA) content serves as a key property. When PONA is not available, the Bureau of Mines Correlation Index (BMCI) is used. Other properties like specific gravity, ASTM distillation, viscosity, refractive index. Conradson Carbon, and Bromine Number are also used to characterize the feed. In recent years even nuclear magnetic resonance spectroscopy has been... 

Even if the process were at steady state, tensile strength, a key property would still reflect some variation. Steady state, or stable operation of any process, has associated with it a characteristic variation. Superimposed on this is the testing method, which is itself a process with its own characteristic variation. The observed variation is a composite of these two variations. 

---