Strength resistivity

Although thermal performance is a principal property of thermal insulation (13—15), suitabiHty for temperature and environmental conditions compressive, flexure, shear, and tensile strengths resistance to moisture absorption dimensional stabiHty shock and vibration resistance chemical, environmental, and erosion resistance space limitations fire resistance health effects availabiHty and ease of appHcation and economics are also considerations. 

Diverse appHcations for the fabric sometimes demand specialized tests such as for moisture vapor, Hquid transport barrier to fluids, coefficient of friction, seam strength, resistance to sunlight, oxidation and burning, and/or comparative aesthetic properties. Most properties can be deterrnined using standardized test procedures which have been pubHshed as nonwoven standards by INDA (9). A comparison of typical physical properties for selected spunbonded products is shown in Table 2. 

Other properties, eg, strength, resistivity, heat capacity, and thermal expansion, are given in the reference (2,4) from which this table is compiled. 

Fusion Reactors. The development of fusion reactors requires a material exhibiting high temperature mechanical strength, resistance to radiation-induced swelling and embrittlement, and compatibUity with hydrogen, lithium and various coolants. One aUoy system that shows promise in this appHcation, as weU as for steam-turbine blades and other appHcations in nonoxidizing atmospheres, is based on the composition (Fe,Co,Ni)2V (30). 

Electrical Properties Traditionally plastics have established themselves in applications which require electrical insulation. PlFt and polyethylene are among the best insulating materials available. The material properties which are particularly relevant to electrical insulation are dielectric strength, resistance and tracking. 

The electneal properties of PTFE are dominated by its extremely tow dielectric constant (2.1) This value is invanant over a broad range ot temperatures (- 40 to 250 °C) and frequencies (5 Hzto 10 GHz). Smularly, PTFE has an unusually low dissipation factor, which is also quite mdependent of temperature and frequency fhis behavior results from the high degree of dipolar symmetry of the perfluonnated and unbranched chains The dielectnc strength, resistivity, and arc resistance are very high... 

Clear, transparent, colorless, good weatherability, good impact strength, resistant to dilute basic and acidic solutions easily colored good mechanical and thermal properties good fabricability poor abrasion resistance compared to glass... 

PTFE is produced by the free radical polymerization process. While it has outstanding thermal and corrosive resistance, it is a marginal engineering material because it is not easily machinable. PTFE has low tensile strength, resistance to wear, and low creep resistance. Molding powders are processed by press and sinter methods used in powder metallurgy. It can also be extruded using ram extruder techniques. 

Bingham plastic Plastic that does not flow until the external stress exceeds a critical threshold value, coefficient of expansion Change in dimensions per degree of temperature, compression strength Resistance to crushing forces. 

Physico-Chemical Properties. The industrial applications of chrysotile fibers were developed taking advantage of their particular combination of properties fibrous morphology, high tensile strength, resistance to heat and corrosion, low electrical conductivity, and high friction coefficient In many applications, the surface properties of the fibers also play an important role in such cases, a distinction between chrysotile and amphiboles can be... 

Most siloxane polymers are excellent insulators, and electrical properties relevant to this characteristic are also much studied. Examples are resistivity, dielectric constant, dielectric losses, dielectric strength (resistance to electrical breakdown), and power factors.16... 

Continuous coating is a well-established process in the non-woven industry. Non-woven textiles reach their final product quality tensile strength, resistance against humidity or surface structure only after the application of appropriate additives to the surface or interior of the textile. In principle, a number of methods are convenient, as shown in Figure 4.107 [167]. 

The mechanical properties of polymers can be expressed in a number of ways. Tensile modulus describes the stiffness of a material and provides information about its potential usefulness. Toughness is defined as the work required to elongate a sample to the breaking point. Polymers with high impact strength resist cracking or breaking when struck by a hard object. 

Kevlar body armor works by catching a bullet in a multilayer web of woven fabrics. Kevlar s extraordinary strength resists tearing and cutting, allowing the stressed fibers to absorb and disperse the impact to other fibers in the fabric. 

---