Radiation, gamma-, resistance

It is characterized by high strength and good impact resistance, and retains its physical properties at temperatures up to 260°C. Its radiation (gamma) resistance is good. 

Figure 5.37 depicts the basic set up of a wireline logging operation. A sonde is lowered downhole after the drill string has been removed. The sonde is connected via an insulated and reinforced electrical cable to a winch unit at the surface. At a speed of about 600m per hour the cable Is spooled upward and the sonde continuously records formation properties like natural gamma ray radiation, formation resistivity or formation density. The measured data is sent through the cable and is recorded and processed in a sophisticated logging unita the surface. Offshore, this unit will be located in a cabin, while on land it is truck mounted. In either situation data can be transmitted in real time via satellite to company headquarters if required. 

Fluorocarbon elastomers, particularly copolymers of HFP and VDF, are cross-linked by low-level y radiation (up to 20 Mrad) in the same fashion as PVDF. Radiation degradation of a VDF-HFP copolymer was studied by Zhong and Sun.35 Their finding was that there is a linear relationship between the dose and the weight loss of the polymer. Fluorocarbon elastomers based on copolymers of IFF and propylene were found to be more resistant to y radiation than Viton elastomers.36 Cross-linking of VDF-HFP, VDF-TFE, and tetrafluoroethylene-propylene (TFE/P) copolymers as well as of terpolymers VDF-HFP-TFE by ionizing radiation (gamma... 

The theoretical equations for scissioning and crosslinking can be used to correlate the results of lithographic behavior of thin films on irradiation. The same deviations can be expected that are found wheat the equations are used for bulk samples exposed to gamma radiation. Positive resists of the type considered here depend on a change in dissolution rate, R, with polymer molecular weight, M. The form of the relationship between R and M is still a matter of some controversy. 

Styrene butadiene rubber (SBR)/poly(ethylene-co-vinyl acetate (EVA) blends were compatibilized with SEBS-g-MA and further gamma irradiated to evaluate their aging resistance toward radiation. The resistance of the blends to gamma irradiation is better for those that contain higher proportions of EVA. ... 

The most common form of crystalline alumina is corundum, which has a rhombohedral Bravais lattice with a space group R-3c. These materials have been used in energy storage, alkali metal thermal-to-electric conversion cells, and gas sensors. In recent years, it has been reported that alumina can also reduce heat, humidity, light, ozone and gamma radiation, flame resistance, and the crack growth in NR. ... 

Medical and health-care related appHcations consume about 21,000 t of polycarbonate aimuaHy. Polycarbonate is popular because of its clarity, impact strength, and low level of extractable impurities. Special grades have been developed to maintain clarity and resistance to yeHowing upon gamma radiation sterilization (qv) processes. Leisure and safety appHcations are many and varied, accounting for about 22,000 t of consumption aimuaHy. The... 

PC—copolyester better processibihty, hydrolytic, and gamma radiation resistance than PC sterilizable apphcations 43,109... 

Radiation Resistance. Polysulfones exhibit resistance to many electromagnetic frequencies of practical significance, including microwave, visible, and infrared. Especially notable is the excellent resistance to microwave radiation, which has contributed to the excellent fit of polysulfones in cookware appHcations. Polysulfone also shows good resistance to x-rays, electron beam (24), and gamma (25,26) radiation under many practical appHcation conditions. 

Polysulfones also offer desirable properties for cookware appHcations, eg, microwave transparency and environmental resistance to most common detergents. Resistance to various sterilizing media (eg, steam, disinfectants, and gamma radiation) makes polysulfones the resin family of choice for many medical devices. Uses in the electrical and electronic industry include printed circuit boards, circuit breaker components, connectors, sockets, and business machine parts, to mention a few. The good clarity of PSF makes it attractive for food service and food processing uses. Examples of appHcations in this area include coffee decanters and automated dairy processing components. 

There are several schemes for nondestructive evaluation. Changes in electrical resistance can be used to follow corrosion. Radiographic techniques involving X-rays and gamma rays have been applied. Transmitted radiation as well as back scattered radiation have been used. 

Gamma hexachlorocyclohexane, radiation resistance, 196 Gamma-rays, 188, 193, 194, 197, 202 Gamma-space, 320 Gas hydrates, 3, 20, 22, 25, 34 mechanism of formation, 4 thermodynamic properties, 15 x-ray work, 3... 

Precision injection molding where feasible, gamma radiation resistant formulations, and improved production traceability and quality. 

The dependence of the volatile product yield with structure can be a very sensitive probe of radiation resistance and the protective effect of aromatic rings. G(H ) was observed to decrease from 5.6 to 0.038 for cyclohexane (3) and benzene (A) after gamma irradiation at ambient temperature. Since all polymers under investigation contained the sulfone moiety, G(SO ) (Table III) is an ideal probe for radiation resistance for this series. 

The increase in the modulus for Bis A PSF and Hq/Bp PSF with irradiation indicated that crosslinking predominated for both polymers and that the crosslink structures were probably basically similar. Hq/Bp(50) PSF was considerably more radiation resistant than Bis-A PSF, as shown by the rate of decrease in the elongation at failure. For both polymers, there was an initial rapid decrease in the elongation at failure followed by a slower decrease. This effect was also demonstrated by the variation in the fracture toughness (KI(.) with irradiation for Bis-A PSF. This work with cobalt-60 gamma radiation complements earlier studies of these materials using high dose rate electron beam irradiation (6). 

The resistance to gamma radiation is excellent without significant degradation after more than 1000 Mrad, exceeding even the behaviour of polystyrene. With alpha and beta radiations, resistance would be higher than 10 000 Mrad. 

The resistance to gamma radiation is good without significant degradation after 500 Mrad tensile strength retention is 94%. 

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