Irradiation tensile strength

Keywords Polymeric membrane, phase inversion, hollow fiber, electrospimiing, modification of membranes, graft polymerization, mixed matrix membrane, UV irradiation, tensile strength... 

In air, PTFE has a damage threshold of 200—700 Gy (2 x 10 — 7 x 10 rad) and retains 50% of initial tensile strength after a dose of 10" Gy (1 Mrad), 40% of initial tensile strength after a dose of 10 Gy (10 lad), and ultimate elongation of 100% or more for doses up to 2—5 kGy (2 X 10 — 5 X 10 rad). During irradiation, resistivity decreases, whereas the dielectric constant and the dissipation factor increase. After irradiation, these properties tend to return to their preexposure values. Dielectric properties at high frequency are less sensitive to radiation than are properties at low frequency. Radiation has veryHtde effect on dielectric strength (86). 

Figure 10 (a) Percent elongation at break (Cb), and (b) tensile strength (o-b) versus irradiation time for polystyrene films O-control -2,4-DHBP -2H-4MBP -2H-4BBP X-DHBP-F A-HMBP-F and Q-HBBP-F. 

Figure 11 (a) Tensile strength (TS), and (b) elongation at break (EB) versus irradiation time for PMMA films X-control ... 

Clay hllers were surface modihed with TMPTA or triethoxyvinyl silane (TEVS) followed by EB irradiation by Ray and Bhowmick [394]. Both the untreated and treated fillers were incorporated in an ethylene-octene copolymer. Mechanical, dynamic mechanical, and rheological properties of the EB-cured unfilled and filled composites were studied and a significant improvement in tensile strength, elongation at break, modulus, and tear strength was observed in the case of surface-treated clay-filled vulcanizates. Dynamic mechanical studies conducted on these systems support the above findings. 

FIGURE 31.13 (a) Plot showing the stress-strain behavior of various irradiated rubbers, (b) Plot showing the variation of tensile strength and modulus of rubbers irradiated with different doses, (c) Plot showing the variation of hysteresis loss, set, and elongation at break of irradiated fluorocarbon rubbers. (From Banik, I. and Bhowmick, A.K., Radial. Phys. Chem., 54, 135, 1999. With permission.)... 

PCTFE is less sensitive than PTFE to high-energy radiation. For example, after a SOMrad irradiation, the tensile strength decay is 50%. 

Lakritz et al. (32) reported that radiation doses of less than 10 kGy (at 0 to 4 C) produced minimal changes in the micro structure of bovine longissimus dorsi muscle. At doses of 30 kGy or higher, myofibril fragmentation and decreased tensile strength were noted. Lakritz and Maerker (33) reported reductions of 8% and 42% in the activities of lysosomal enzymes and acid phosphatase of irradiated (10 kGy) bovine longissimus dorsi muscle tissue. 

In general, copolymers cross-link more readily than polyamide PA 66. Mechanical properties of polyamides are modified by irradiation, as seen by reduced tensile strength (50% loss when irradiated in air, 16% under vacuum). Aromatic polyamides retain strength better than aliphatic polyamides. ... 

Tensile strength of radiation cured purified natural rubber, o, sulfur A, peroxide , EB irradiation in nitrogen at 2.5 kGy/s. (Bohm, G. G. A., and Tveekrem, J. O., Rubb. Chem. Technol., 55 3, p. 620. Reprinted with permission from Rubber Division, ACS.)... 

The prevulcanization of natural rubber in latex form has also been a subject of much investigation. The cross-linking mechanism is not yet fully understood, but the water apparently plays a major role in it. Irradiation results in the cross-linking of the rubber molecules and in coarsening of the latex particles. A process of cross-linking of natural rubber latex has been developed to the point that it can be used for an industrial-scale application. The irradiation is performed in aqueous media by electron beam without a prorad (sensitizer) at a dose of 200 kGy (20 Mrad) or in the presence of n-butyl acrylate at considerably lower doses, typically 15 kGy. The cross-linked film exhibits physical properties comparable to those obtained from sulfur cured (vulcanized) film. As an alternative, the addition of a variety of chloroal-kanes makes it possible to achieve a maximum tensile strength with radiation doses of less than 5 Mrad (50 kGy). ... 

Irradiation of carbon-black-reinforced polychloroprene compounds produced a maximum tensile strength of 20 MPa (2,900 psi) at a dose of 20 Mrad (200 kGy), which is a value obtained typically from chemically cured compounds. The addition of 20 phr of N,N -hexamethylene-bis methacrylamide as a prorad in the above compound produced a tensile strength of 18 MPa (2,610 psi) at a dose of 7 Mrad (70 kGy). Further addition of 6 phr of hexachlo-roethane caused the deterioration of the tensile strength by 50% at the 7 Mrad (70 kGy) dose. ... 

When irradiating a 1 1 blend of polychloroprene and poly(butadiene-acry-lonitrile) (NBR) reinforced by 50 phr furnace black and containing 5-15 phr of tetramethacrylate of bisglycerol phtalate, the product exhibited a tensile strength of 20 MPa (2,900 psi) at a dose of 15 Mrad (150 kGy) with values of elongation at break in the range of 420-480%. These values are equal to or better than those obtained from similar compounds cured chemically. ... 

Tensile Strength Data from Selected EB-Irradiated Elastomers... 

FIGURE 5.7 Tensile strength of radiation-cured purified natural rubber. Legend = sulfur T = peroxide = EB irradiation. (Bohm, G.G.A. and Tveekram, J.ORubber Chem. Technol. Vol. 55, No. 3 (1982). With permission.)... 

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