Physical toughness

PROPERTIES OF SPECIAL INTEREST Resistance to penetration by natural wood oils, film clarity, heat sealability, adhesion to a variety of surfaces, chemical and solvent resistance, physical toughness. 

Polychloroprene is a multipurpose elastomer that has a good balance or properties that include outstanding physical toughness and wider short-term/long-term... 

One of its earliest applications, in fact, was the primary insulator on computer hookups used in back panels and installed by high speed, automatic wiring machines While satisfactory electrical properties of the polymer were important, automatic wiring equipment also required a wire insulation material of exceptional physical toughness. KYNAR pvDF easily fit this requirement. 

Oxide layers formed by some metals in the atmosphere are most useful if they are physically tough and damage resistant. In any case, if damage should occur, the protective layer rapidly reforms. Thicker coatings may be obtained by anodizing, i.e. by anodically polarizing the material by electrolysis with some cathode in a suitable electrolyte. 

Nylon-6,6 [32131 -17-2J is a tough, translucent white, semiciystalline, high melting (T , = 265 C) material. The common physical properties ate shown in Table 9, and principal producers woddwide in Table 10, for nylon-6,6 and other commercial polyamides. 

Nylon-6 [25038-54-4] was first made in 1899 by heating 6-aminohexanoic acid (143), but its commercially feasible synthesis from caprolactam was discovered by Paul Schlack at 1. G. Farbenindustrie in 1938. Like nylon-6,6, it is a tough, white translucent, semicrystalline sofld, but melts at a lower temperature (T = 230° C. The physical properties and primary producers of nylon-6 are Hsted in Tables 9 and 10, respectively. 

The durabihty and versatility of steel are shown by its wide range of mechanical and physical properties. By the proper choice of carbon content and alloying elements, and by suitable heat treatment, steel can be made so soft and ductile that it can be cold-drawn into complex shapes such as automobile bodies. Conversely, steel can be made extremely hard for wear resistance, or tough enough to withstand enormous loads and shock without deforming or breaking. In addition, some steels are made to resist heat and corrosion by the atmosphere and by a wide variety of chemicals. 

In addition to chemical analysis a number of physical and mechanical properties are employed to determine cemented carbide quaUty. Standard test methods employed by the iadustry for abrasive wear resistance, apparent grain size, apparent porosity, coercive force, compressive strength, density, fracture toughness, hardness, linear thermal expansion, magnetic permeabiUty, microstmcture, Poisson s ratio, transverse mpture strength, and Young s modulus are set forth by ASTM/ANSI and the ISO. 

The modem interest in composite materials can be traced to the development of BakeHte, or phenoHc resin, in 1906. BakeHte was a hard, brittle material that had few if any mechanical appHcations on its own. However, the addition of a filler— the eadiest appHcations used short cellulose fibers (2)—yielded BakeHte mol ding compounds that were strong and tough and found eady appHcations in mass-produced automobile components. The wood dour additive improved BakeHte s processibiHty and physical, chemical, and electrical properties, as weU as reducing its cost (3,4). 

The polysulfide impression materials can be formulated to have a wide range of physical and chemical characteristics by modifying the base (polysulfide portion), and/or the initiator system. Further changes may be obtained by varying the proportion of the base to the catalyst in the final mix. Characteristics varied by these mechanisms include viscosity control from thin fluid mixes to heavy thixotropic mixes, setting-time control, and control of the set-mbber hardness from a Shore A Durometer scale of 20 to 60. Variations in strength, toughness, and elasticity can also be achieved. 

In order to improve the physical properties of HDPE and LDPE, copolymers of ethylene and small amounts of other monomers such as higher olefins, ethyl acrylate, maleic anhydride, vinyl acetate, or acryUc acid are added to the polyethylene. Eor example, linear low density polyethylene (LLDPE), although linear, has a significant number of branches introduced by using comonomers such as 1-butene or 1-octene. The linearity provides strength, whereas branching provides toughness. 

Although the prime function of plasticisers in cellulose acetate is to bring the processing temperature of the compound below the polymer decomposition temperature, it has additional values. An increase in the plasticiser content will reduce the melt viscosity at a given temperature and simplify processing. The physical properties of the finished product will be modified, increasing toughness... 

When the stress that can be bom at the interface between two glassy polymers increases to the point that a craze can form then the toughness increases considerably as energy is now dissipated in forming and extending the craze structure. The most used model that describes the micro-mechanics of crazing failure was proposed by Brown [8] in a fairly simple and approximate form. This model has since been improved and extended by a number of authors. As the original form of the model is simple and physically intuitive it will be described first and then the improvements will be discussed. 

The data also demonstrate that the addition of the thermoplastic, PMMA, does not have the significant effect on the toughness or adhesion properties as does the addition of the rubber, Vamac B-124. Clearly, the physical properties of the polymeric additive determine the magnitude of the adhesive physical property modifications, which result from their addition to an alkyl cyanoacrylate monomer. 

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