XPS STUDIES ON RADIATION-INDUCED STRUCTURAL-CHANGES IN THE COPOLYMER OF TETRAFLUOROETHYLENE AND ETHYLENE

In this work, the radiation-induced structural changes in the copolymer of tetrafluoroethylene and ethylene (F-40) were studied by X-ray photoelectron spectroscopy (XPS). During irradiation, some CF2 groups in the polymer were found to have been converted into carbon structures that bonded indirectly with fluorine atoms.

RADIATION STABILITY OF PERFLUOROETHYLENE PROPYLENE COPOLYMER

The gel content of crosslinked perfluoroethylene-propylene copolymer was obtained by extraction with fluoro-chloro oil. It was then treated by the Charlesby-Pinner equation. The results obtained revealed that both the gelation dose and the ratio of fracture to crosslinking density decreased with increasing irradiation temperature.

RADIATION EFFECTS ON CRYSTALLINE POLYMERS .1. GAMMA-RADIATION-INDUCED CROSS-LINKING AND STRUCTURAL CHARACTERIZATION OF POLYETHYLENE OXIDE

By using WAXD, DSC and gel fraction determination techniques, the mechanism of radiation crosslinking of polyethylene oxide (PEO) was explored, and the dependence of aggregated state on the chemical reaction and physical structure was also discussed. It was found that just like other semi-crystalline polymers, the state of aggregation of the specimen has a profound influence on the radiation effects on PEO. On the contrary, the crystalline structure of the specimen is severely affected with the increase in radiation dose and eventually amorphortized when subjected to an extremely high radiation dose.

STUDIES ON RADIATION-INDUCED LOSS OF WEIGHT OF A COPOLYMER OF TETRAFLUOROETHYLENE AND HEXAFLUOROPROPYLENE

The radiation-induced loss of weight of F-46 was found to be proportional to irradiation dose and affected markedly by irradiation temperature.

RADIATION-INDUCED CROSS-LINKING OF AROMATIC POLYMERS WITH A CARDO GROUP

The effects of irradiation on some members of the family of aromatic polymers with a cardo group, such as polyetherketone with a cardo group (PEK-C) and polyethersulfone with a cardo group (PES-C), were studied. It was found that PEK-C and PES-C can be crosslinked by irradiation under vacuum. Moreover, it was also found that the intensity of the shake-up peak of x-ray photoelectron spectroscopy (XPS) for PEK-C and PES-C varies with irradiation dose. Gelation doses (Rg) of PEK-C and PES-C were estimated from the XPS shake-up peak.

XPS STUDY OF RADIATION CROSS-LINKED COPOLYMER OF TETRAFLUOROETHYLENE WITH HEXAFLUOROPROPYLENE

In this work the radiation-induced structural changes in F-46 were studied by XPS. In carbon-1s spectra of a highly crosslinked F-46 sheet, the slight increase observed in relative area under the peak due to CF3 was explained by the radiation-induced scission of polymer chains. The peak at 287.6 eV appearing in the spectra caused by ionizing radiation was attributed to carbon structures without primary fluorine substituents, in both branching and unsaturated structures, while that at 289.3 eV was assigned to = CF groups in mid-chain double bonds.

RADIATION-INDUCED CROSS-LINKING OF POLY(METHYL METHACRYLATE)-POLY(ETHYLENE OXIDE) BLEND

Radiation-induced crosslinking of poly(methyl methacrylate) (PMMA)-poly(methylene oxide) (PEO) blends was studied. It was found that PMMA in PMMA-PEO blend can be crosslinked in the range of certain doses (1 approximately 20 x 10(4) Gy) and composition (PMMA% = 30 approximately 70) under the absence of oxygen. Moreover, it was also found that the crosslinking degree of PMMA in the blend in which the content of PMMA is 70% is the largest. The crosslinking degree of PMMA in the blend is closely related with the polymer miscibility. The crosslinking degree of the blend prepared at 60-degrees-C is far higher than one at ambient temperature.

STUDIES ON RADIATION EFFECTS OF PTFE .2. RADIATION-INDUCED STRUCTURAL-CHANGES AND THE TEMPERATURE EFFECT

In this work PTFE sheets irradiated with gamma-rays at 150-degrees-C and 200-degrees-C were studied using x-ray photoelectron spectroscopy (XPS). The main structural changes in PTFE due to radiation are the formation of CF3 and CF groups. An irradiation temperature dependence of the relative content of the three kinds of groups in irradiated PTFE was observed. The CF3 groups, especially when irradiation is carried out a lower temperatures, can defluorinate in the same manner as previosly reported for CF2 groups. The CF groups, on the other hand, are observed to increase with increasing irradiation dose and irradiation temperature; the latter was explained as due to an increase in branching structures.

CHARACTERIZATION OF GAMMA-RADIATION CROSS-LINKED CRYSTALLINE POLYMERS BY CRYSTALLIZATION TEMPERATURE

The effect of gamma-radlatlon on plain crystalline polymers and crystalline polymers containing different amounts of difunctional monomer both in vacuum and in air at room temperature has been investigated with DSC. It was found that the crystallization temperature T_c of crosslinked sample measured on DSC at a constant cooling rate decreases with increasing radiation dose. The difference between T_c before and after crosslinking (T_(c_0)-T_(c_R)) is linearly related to the radiation dose for plain polymer....