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ABSTRACT PTFE with a 15% addition of graphite was subjected to irradiation using an electron beam of 10 MeV energy with absorbed doses of 26, 52, 78, 104, and 156 kGy. The effect of electron-beam irradiation on the mechanical, sclerometic, and tribological properties, the crystallinity degree, and the morphology of the polymer surface was examined. It was found that the modification through irradiation entailed a gradual increase in the degree of crystallinity, which had a direct influence on the mechanical properties. An increase in the hardness, Young's modulus, and compressive strength of the polymer irradiated with an electron beam was also demonstrated. The electron-beam irradiation reduced the value of components of the work-of-indentation, showing the growing resistance to deformation. An analysis of the scratch test parameters showed a reduced depth of penetration of the indenter into the material, proportionally to the irradiation value, at relatively constant values of the scratch depth after scratching load removal. A stereometric analysis of the scratch traces on the material allowed to determine coefficients of the wear micromechanism, β, and resistance to wear, Wβ. It was found that after irradiation (especially with a dose of 4 × 26 kGy), a significant quantity of the material showed traces of ploughing, which meant a positive effect on the wear mechanism. The value of the wear resistance coefficient Wβ for PTFE subjected to the absorbed irradiation dose increased intensively, which portended a significant reduction of the tribological wear compared to the nonirradiated material. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42348. [ABSTRACT FROM AUTHOR]

To improve the functional properties of polyethylene in a polymer-metal kinematic system, ultra-high-molecular-weight polyethylene (UHMWPE) was subjected to light deformation by uniaxial compression [permanent true strain ( e f) = 0.14-0.32] and postdeformation electron-beam irradiation (with a dose of 26-52 kGy). X-ray examinations demonstrated that no significant reorientation of the lamellar structure occurred upon compression. The textures of all of the samples, except for the sample deformed at e f = 0.32, were nearly random. In the exception, a very weak axial texture developed. However, the treatment applied (deformation and electron-beam irradiation) significantly changed the structure of the material. A considerable increase in the crosslinked fraction and the crystalline band absorption in the Fourier transform infrared spectra were observed in the modified samples. This indicated a noticeable increase in the degree of spatial ordering within a structure, although the overall crystallinity increased only slightly. The effect of such restructuring was evidenced by microscopic observations of the near-surface layer of the UHMWPE samples subjected to unidirectional sliding interaction with a CoCr alloy for 100 h (in a block-ring tribological system). It was found that for the predeformed ( e f = 0.14-0.21) and electron-irradiated (dose of 52 kGy) samples, the operational load imposed on the system resulted in a considerable reduction in the thickness of the plastically deformed near-surface layer and in a decreasing amount of lamellae oriented flat-on compared to the neat unmodified UHMWPE subjected to the same test. The recorded tribological wear (mass decrement) decreased up to fivefold in comparison to that of the initial material. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012 [ABSTRACT FROM AUTHOR]

This research investigated the effect of irradiation with an electron beam energy of 10 MeV in doses of 26–156 kGy on polytetrafluoroethylene (PTFE) with a 15% and 20% graphite additive. The research has shown that mechanical (compression strength, hardness, and Young's modulus) and sclerometric (coefficient of wear micromechanism and coefficient of resistance to wear) properties improve and tribological wear decreases as graphite content increases. Electron beam irradiation increases the degree of crystallinity of both materials to a similar extent. However significant differences in the improvement of all examined properties have been demonstrated for PTFE with higher (20%) graphite content subjected to the electron beam irradiation. This polymer is characterized by higher hardness and Young's modulus, reduced susceptibility to permanent deformation, higher elasticity, compression strength, and above all, a nearly 30% reduction in tribological wear compared to PTFE with a 15% graphite additive. The most advantageous properties can be obtained for both of the examined composites after absorbing a dose of 104 kGy. The obtained results hold promise for the improvement of the operational life of friction couples which do not require lubrication, used for example in air compressors and engines, and for the possibility of application of these modified polymers. In particular PTFE with 20% graphite content, in the nuclear and space industry. [ABSTRACT FROM AUTHOR]

This study analyzed the effects of irradiation of polytetrafluoroethylene (PTFE) containing 40% of bronze using an electron beam with energy of 10 MeV. Dosages from 26 to156 kGy (2.6–15.6 Mrad) were used. The impact of a high-energy electron beam on the thermal, spectrophotometric, mechanical, and tribological properties was determined, and the results were compared with those obtained for pure PTFE. Thermal properties studies showed that such irradiation caused changes in melting temperature Tm and crystallization temperature Tc, an increase in crystallization heat ∆Hc, and a large increase in crystallinity χc proportional to the absorbed dose for both polymers. The addition of bronze decreased the degree of crystallinity of PTFE by twofold. Infrared spectroscopy (FTIR) studies confirmed that the main phenomenon associated with electron beam irradiation was the photodegradation of the polymer chains for both PTFE containing bronze and pure PTFE. This had a direct effect on the increase in the degree of crystallinity observed in DSC studies. The use of a bronze additive could lead to energy dissipation over the additive particles. An increase in hardness H and Young's modulus E was also observed. The addition of bronze and the irradiation with an electron beam improved of the operational properties of PTFE. [ABSTRACT FROM AUTHOR]