Combination of properties

One way of generating new properties is by combination of properties. For instance, the counting function of BE and the volume of the VP is defined as 

Note that although we have combined two properties, we still have a singlet generalized MDF. A related singlet generalized MDF which conveys similar information to that in (2.111), but is simpler for computational purposes, is constructed by the combination of BE and CN, i.e. 

112) the firs 8 on the rhs is a Dirac delta function, whereas the second is a Kronecker delta function. 

The general procedure of defining generalized MDFs is now clear. We first define a property which is a function definable on the configurational space, and then introduce its distribution function in the appropriate ensemble. Examples of some of these may be found in Ben-Naim (1973a and 1974). 

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SAN resins are rigid, hard, transparent thermoplastics which process easily and have good dimensional stability—a combination of properties unique in transparent polymers. 

Film or sheet generally function as supports for other materials, as barriers or covers such as packaging, as insulation, or as materials of constmction. The uses depend on the unique combination of properties of the specific resins or plastic materials chosen. When multilayer films or sheets are made, the product properties can be varied to meet almost any need. Further modification of properties can be achieved by use of such additives or modifiers as plasticizers (qv), antistatic agents (qv), fire retardants, sHp agents, uv and thermal stabilizers, dyes (qv) or pigments (qv), and biodegradable activators. 

Biaxial Orientation. Many polymer films require orientation to achieve commercially acceptable performance (10). Orientation may be uniaxial (generally in the machine direction [MD]) or biaxial where the web is stretched or oriented in the two perpendicular planar axes. The biaxial orientation may be balanced or unbalanced depending on use, but most preferably is balanced. Further, this balance of properties may relate particularly to tensile properties, tear properties, optical birefringence, thermal shrinkage, or a combination of properties. A balanced film should be anisotropic, although this is difficult to achieve across the web of a flat oriented film. 

Different resins have been developed for use in different reduction—ratio appHcation ranges (111,112). The powders suitable for high reduction—ratio appHcations, such as wire coatings, are not necessarily suitable for the medium reduction—ratio appHcations, such as tubings, or the low reduction—ratio appHcations, such as thread-sealant tapes or pipe liners. AppHcations and processing techniques are being used, which utilize the unique combination of properties offered by PTFE in fine powder form (113—115). 

Copolymeis of ethylene [74-85-1] and tetiafluoioethylene [116-14-3] (ETFE) have been alaboiatory curiosity for more than 40 years. These polymers were studied in connection with a search for a melt-fabricable PTFE resin (1 5) interest in them fell with the discovery of TFE—HFP (FEP) copolymers (6). In the 1960s, however, it became evident that a melt-fabricable fluorocarbon resin was needed with higher strength and stiffness than those of PTFE resins. Earlier studies indicated that TFE—ethylene copolymers [11939-51 -6] might have the right combination of properties. Subsequent research efforts (7) led to the introduction of modified ethylene—tetrafluoroethylene polymer [25038-71-5] (Tefzel) by E. I. du Pont de Nemours Co., Inc, in 1970. 

Because of its excekent combination of properties, processibkity, and relatively low price compared to other fluoropolymers, PVDF has become the largest volume fluoropolymer after PTFE consumption in the United States has grown from zero in 1960 to about 6200 metric tons in 1991 (186). About 49% of the consumed volume is PVDF modified by copolymerization with 5—12-wt % HFP to enhance flexibkity. In 1992, Hst price for homopolymer powders was 15.32/kg, and for pekets 15.42/kg the reported market price was 14.09—14.22/kg (187). In the United States, almost ak PVDF is suppHed by Ausimont USA, Inc., Elf Atochem North America, Inc., and Solvay Polymers, Inc. Ausimont and Elf Atochem are producers Solvay is an importer of the resin. Smak amounts of resin are imported from Germany by Huls America, Inc, and from Japan by Kureha Chemical Industry Co., Ltd. PVDE producers and their trademarks are Hsted in Table 4. 

Uses of gelatin are based on its combination of properties reversible gel-to-sol transition of aqueous solution viscosity of warm aqueous solutions abUity to act as a protective coUoid water permeabUity and insolubUity in cold water, but complete solubUity in hot water. It is also nutritious. These properties are utilized in the food, pharmaceutical, and photographic industries. In addition, gelatin forms strong, uniform, clear, moderately flexible coatings which readily sweU and absorb water and are ideal for the manufacture of photographic films and pharmaceutical capsules. 

Most of the laminates used for rigid printed circuit boards have been classified, by the National Electrical Manufacturers Association (NEMA), according to the combination of properties that determine the suitabiHty of a laminate for a particular use. Eiber reinforcements make laminate-effective properties orthotropic. 

Tris(2-ethylhexyl) phosphate shows good compatibiUty with PVC and also imparts good low temperature performance in addition to good fire retardancy. 2-Ethyhexyl diphenyl phosphate has widespread use in dexible PVC appHcations due to its combination of properties of plasticizing efficiency, low temperature performance, migration resistance, and fire retardancy. 

The main benefit of the Dow process was control of the polymer architecture. The polymer from the self-condensation process possessed a linear stmcture, but there were other difficulties. The monomer was cosdy and removal of the cuprous bromide by-product was difficult (17) ultimately, scale-up difficulties terrninated the Dow PPS development. However, there was a growing recognition that PPS was an attractive polymer with an excellent combination of properties. 

Mixtures of isomeric amyl alcohols (1-pentanol and 2-methyl-1-butanol) are often preferred because the different degree of branching imparts a more desirable combination of properties they are also less expensive to produce commercially. One such mixture is a commercial product sold under the name Primary Amyl Alcohol by Union Carbide Chemicals and Plastics Company Inc. 

Sulfamic acid has a unique combination of properties that makes it particularly well suited for scale removal and chemical cleaning operations, the main commercial appHcations. Sulfamic acid is also used in sulfation reactions, pH adjustment, preparation of synthetic sweeteners (qv), and a variety of chemical processing appHcations. Salts of sulfamic acid are used in electroplating (qv) and electroforrning operations as well as for manufacturing flame retardants (qv) and weed and hnish killers (see Herbicides). 

Citric acid is utilized in a large variety of food and industrial appHcations because of its unique combination of properties. It is used as an acid to adjust pH, a buffer to control or maintain pH, a chelator to form stable complexes with multivalent metal ions, and a dispersing agent to stabilize emulsions and other multiphase systems (see Dispersants). In addition, it has a pleasant, clean, tart taste making it useful in food and beverage products. 

Acrylic Resins. The first synthetic polymer denture material, used throughout much of the 20th century, was based on the discovery of vulcanised mbber in 1839. Other polymers explored for denture and other dental uses have included ceUuloid, phenolformaldehyde resins, and vinyl chloride copolymers. Polystyrene, polycarbonates, polyurethanes, and acryHc resins have also been used for dental polymers. Because of the unique combination of properties, eg, aesthetics and ease of fabrication, acryHc resins based on methyl methacrylate and its polymer and/or copolymers have received the most attention since their introduction in 1937. However, deficiencies include excessive polymerization shrinkage and poor abrasion resistance. Polymers used in dental appHcation should have minimal dimensional changes during and subsequent to polymerization exceUent chemical, physical, and color stabiHty processabiHty and biocompatibiHty and the abiHty to blend with contiguous tissues. 

Properties. The principal advantages of anthraquiaone dyes are brightness and good fastness properties, but they are both expensive and tinctorially weak. However, they are stiU used extensively, particularly ia the red and blue shade areas, because other dyes caimot provide the combination of properties offered by anthraquiaone dyes, albeit at a price. 

This combination of monomers is unique in that the two are very different chemically, and in thek character in a polymer. Polybutadiene homopolymer has a low glass-transition temperature, remaining mbbery as low as —85° C, and is a very nonpolar substance with Htde resistance to hydrocarbon fluids such as oil or gasoline. Polyacrylonitrile, on the other hand, has a glass temperature of about 110°C, and is very polar and resistant to hydrocarbon fluids (see Acrylonitrile polymers). As a result, copolymerization of the two monomers at different ratios provides a wide choice of combinations of properties. In addition to providing the mbbery nature to the copolymer, butadiene also provides residual unsaturation, both in the main chain in the case of 1,4, or in a side chain in the case of 1,2 polymerization. This residual unsaturation is useful as a cure site for vulcanization by sulfur or by peroxides, but is also a weak point for chemical attack, such as oxidation, especially at elevated temperatures. As a result, all commercial NBR products contain small amounts ( 0.5-2.5%) of antioxidant to protect the polymer during its manufacture, storage, and use. 

The best oxidation inhibitors are not usually the best antio2onants (qv). A disubstituted i ra-phenylenediamine such as AJ-isopropyl-AT-phenyl- -phenylenediamine is often selected for that purpose. -Phenylenediamine derivatives iaterfere with cure chemistry and scorchiness, and can stain objects ia contact with the vulcani2ate (114). On balance, /V-(1,3-dimethy1buty1)-/V-phenyl- -phenylenediamine and phenyl /to1y1- -pheny1enediamines have the best combination of properties. They are less scorchy and provide excellent o2one and heat resistance. Additional protection is gained ia blends with a small amount of EPDM mbber (126). 

The polyetherimide—polysdoxane multiblock copolymers are relatively hard (about 70 on the Shore D scale). Their main appHcation is flame-resistant wire and cable covering (24), where they combine very low flammabiUty with a low level of toxic products in the smoke. This unusual and vital combination of properties justifies their relatively high price, about 37/kg, at a specific gravity of about 1.2. 

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