Outstanding high-temperature properties

Alloys with rhenium, another high melting point metal (3180°C) exhibit outstanding high temperature properties insofar as they have a higher recrystallisation temperature than pure tungsten and are still ductile in the recrystallised condition. Common alloys with rhenium contain 3%, 5% or 26% rhenium. The 3% and 5% alloys combine ductility with reasonable... 

Polyimides have excellent physical properties and are used in applications where parts are exposed to harsh environments. They have outstanding high-temperature properties and their oxidative stability allows them to withstand continuous service in air at tempera-tures of 260°C. Polyimides will burn, but they have self-extinguishing properties. They are resistant to weak acids and organic solvents but are attacked by bases. The polymer also has good electrical properties and resistance to ionizing radiation. A disadvantage of polyimides is their hydrolysis resistance. Exposure to water or steam above 100°C may cause parts to crack. ... 

Polymer derived ceramics have been known for the last four decades and are prepared via solid-state thermolysis of preceramic polymers. They exhibit a unique combination of remarkable properties due to their covalent bonding and amorphous nature. Thus, silicon oxycarbide (SiOC) and silicon carbonitride (SiCN) based ternary PDCs have been shown to possess outstanding high-temperature properties such as stability with respect to crystallization and decomposition, oxidation and corrosion resistance as well as excellent thermomechanical properties (e.g., near zero steady state creep resistance up to temperatures far beyond 1000 °C). Their properties are directly influenced by the chemistry and the architecture of the preceramic precursors, thus there is an enormous potential in tuning the microstructure and properties of the PDCs by using tailored polymers. Furthermore, suitable chemical modification of the preceramic precursors leads to quaternary and multinary ceramics, as it has been shown for instance for silicon boron carbonitride ceramics in the last 25 years, which in some cases exhibit improved properties as compared to those of the ternary materials. 

The next criterion was the selection of materials that would yield the desired mechanical properties. Butyl elastomer (HR), a copolymer of isobutylene with a small amount of isoprene, has outstanding low-temperature properties and very high damping, but has very high creep without cross-linking." It was theorized that a blend of SIBS TPE and butyl elastomer, filled to achieve the required minimum density of 2.4 g cm, would be a promising composite for less-lethal ammu-... 

As can be seen from this figure, the heat-resistance was remarkably improved by the drastic changes in the microstructure from amorphous to polycrystalline structure. Another type of SiC-based fiber, SA fiber (2), has a sintered SiC polycrystalline structure and includes very small amounts of aluminum. This fiber exhibits outstanding high temperature strength, coupled with much improved thermal conductivity and thermal stability compared with the Nicalon and Hi-Nicalon fibers. The fabrication cost of the SA fiber is also reduced to near half of that of the Hi-Nicalon Type S [ 17]. The SA fiber makes SiC/SiC composites even more attractive to the many applications [18]. In the next section, the production process, microstructure and physical properties of the SA fiber are explained in detail. 

Functional perfluoropolyethers11 (Figure 14.7) can also be prepared by direct fluorination in high yields. Difunctional perfluoropolyethers based on fluorinated polyethylene glycol) are of particular interest as possible precursors for elastomers, which should have outstanding high-temperature and low-temperature properties. 

The key properties of high-c/s BR vulcanizates are outstanding low-temperature properties, high elasticity, even at low temperatures, and better wear resistance than all other elastomers. 

Owing to their outstanding properties, silicon carbide fiber reinforced silicon carbide matrix (SiC/SiC) composites have been specified in several applications especially in recent fusion power plant design studies and have been considered internationally in several power plant studies. These characteristics include high-temperature properties and stability, corrosion resistance, as well as low induced radioactivity, quick decay of activity, low afterheat, low atomic number, good fracture resistance and more. 

Another advancement in acrylic adhesives has been in the area of acrylics with improved low temperature properties, sometimes called HI or high impact acrylics. These variants of the technology not only offer outstanding low temperature properties, but also significant heat resistance makes them ideal for applications where product performance over a wide temperature range is required. Formulators have also further advanced the art in the use of ingredients that are nonflammable and have little or no odor. 

Heterocyclic polymers yield materials with outstanding high-temperature performance see Table 7.2 (2). Many of these polymers have ladder or semiladder chemical structures. If one bond in a ladder structure is broken by heat or oxidation, the chain may retain its original molecular weight. If a single carbon atom chain is oxidized, usually the chain is degraded, with concomitant loss of properties. 

There are several commercial thermotropic polyesters that exhibit outstanding high-temperature capabilities. These include (14,15) an increasing number of fibers and high temperature plastics. Similar to the lyotropic liquid crystalline polymers, the thermotropics exhibit unusually low viscosities because of orientation and lack of entanglement. Of course, the orientation serves to improve their mechanical properties. The chemical structure can be varied significantly. 

Glass-reinforced polyethersulfone exhibits outstanding high temperature creep resistance, hydrolysis resistance, and self-extinguishing properties combined with good impact strength and low mold shrinkage. 

PP Good high-temperature properties and outstanding chemical resistance 194 Heat fusion Threading Chemical waste Natural gas Oil field... 

Fully imidized aromatic thermoplastic polyimides (TPI) are linear polymers with good thermomechanical performance, used in high-temperature (>230°C) applications. Pis based on aromatic diamines and dianhydrides exhibit excellent heat resistance. In addition to their outstanding high-temperature resistance (Sancaktar et al. 1984 Sancaktar and Schenck 1985 Sancaktar and Dembosky 1986), toughness and good dielectric properties, low flammability, and high radiation resistance are desirable characteristics for this class of adhesives. 

DMA method), Celazole U-60 also has the highest compressive strength at 57 kpsi.The superior physical properties, high temperature properties and outstanding chemical resistance make Celazole U-60 the world s highest performing plastic material. Typical properties data of Celazole U-60 are summarized in Table 7.2. 

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