Resistivity and Temperature

The isopropylidene linkage imparts chemical resistance, the ether linkage imparts temperature resistance, and the sulfone linkage imparts impact strength. The brittleness temperature of polysulfones is — 100°C. Polysulfones are clear, strong, nontoxic, and virtually unbreakable. They do not hydrolyze during autoclaving and are resistant to acids, bases, aqueous solutions, aliphatic hydrocarbons, and alcohols. 

Oriented polypropylene film (OPP) may be classified as heat-set and non-heat-set, blown and tentered, coextmded and coated. Orientation improves the cold-temperature resistance and other physical properties. Heat-set biaxially oriented polypropylene film (BOPP) is the most widely used protective packagiag film ia the United States. It is used to wrap bakery products, as lamination pHes for potato and com chips, and for pastas and numerous other flexible pouch and wrapping appHcations. Nonheat-set OPP is used as a sparkling, transparent shrink-film overwrap for cartons of candy. 

Chlorendic Acid Polyester These resins have excellent resistance to acids, good resistance to oxidizing acid media and high-temperature resistance, and moderate fire resistance. 

Additives and copolymers have extended the use of PET fibers into areas where the original commodity products had deficiencies, in, for example, soil-resistance, static protection or poor dyeability. Newer members of the polyester family have found applications in markets where more stretchiness or resiliency were desired (using longer aliphatic chains) or to gain higher modulus, temperature resistance and strength (with fully aromatic polymers). 

Poly(butylene terephthalate) (PBT) is a semicrystalline, thermoplastic polyester which is completely analogous to PET except that it has a longer, more flexible butylene chain linkage which imparts a rapid crystallization rate, thus making PBT well suited to injection moulding processes. This polyester is used widely for electrical and electronic components due to its high temperature resistance and good electrical properties (Chapter 8). 

R. D. Ritchie, Symposium on "High Temperature Resistance and Thermal Degradation of Polymers"... 

They are used for their temperature resistance and fire behaviour. 

Figure 27 The low temperature resistivity and susceptibility of a (La,Ba)-Cu-0 sample where a high-Tc was first observed. Re-drawn from Reference 147.

The changes in resistivity with annealing of films deposited from selenourea and selenosulphate baths, as well as evaporated films, were compared [71,72]. Although there were small differences between the various films, no major difference was found. Additionally, the resistivity of as-deposited films, deposited from both selenourea and selenosulphate baths, does not change with time over a period of months in air. However, after annealing in air at 350°C when the resistivity increases, there is a gradual decrease in room-temperature resistivity (and also in photoconductivity response) with time [73], These variations were related to formation of PbSeOs and adsorbed oxygen on the surface of the annealed crystals. 

The presence of aromatic groups in polymers greatly reduces their radiation sensitivity. Aromatic polysulfones are commercially important engineering plastics with high temperature resistance and also show good radiation resistance (16). Development of polymers with improved radiation resistance should be possible by copolymerization of other aromatic structures into the chain. 

TPX is considered a high temperature host polymer, which provides scintillator properties. A modified TPX is manufactured under the brand name THERMOSCIN. The material is temperature resistant and has a relatively high hydrogen content as compared to a conventional scintillation material (20). 

Heubach has developed a process for the alternate precipitation of metal oxides and silicates [3.141 ], [3.142]. A homogenizer is used to disperse the pigment particles during stabilization. Products obtained have a very good temperature resistance and very low lead solubility in acid (< 1 % Pb by DIN 55770, 1986 or DIN/ISO 6713, 1985). 

DATB-HMX Explosive Compositions for High Temperature Resistance and High Energy. They are discussed by B.A.Stott D-A.Sbrocca in conf NAVWEPS Rept 7589 (NOTS TP 2570 (Dec I960)... 

Table I. Room Temperature Resistivities and Thermal Coefficients of Tungsten Bronzes...

High purity binary oxides such as BeO, MgO, AI2O3, Ti02, And stabihzed zirconia are sintered under pressure to produce high density ceramic ware, particularly cracibles and other containers for use in nonferrous metallurgy and other specialized applications where temperature resistance and corrosion are a problem. Titania is also formed in honeycomb arrays for use as catalyst supports. 

---