Surface layer modification of ion bombarded HDPE (original) (raw)
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Ion bombardment of polyethylene—influence of polymer structure
Vacuum, 2007
Polyethylenes of various macromolecular and supermolecular structures were studied from the point of view of their susceptibility to an ion beam treatment. An influence of molecular weight (M w ), molecular weight distribution (M w /M n ) and the degree of branching were compared within the set of low-density polyethylenes (LDPE) studied. An influence of the length of branches was compared between LDPE, linear low-density (LLDPE) and high-density (HDPE) polyethylenes. An influence of the degree of crystallinity and the morphology of a crystalline phase were compared for HDPE samples solidified under various thermal conditions and ultra-high molecular weight polyethylene (UHMWPE). Plate polymer targets $2 mm were bombarded with 100 keV He + or 130 keV Ar + ions (dose of 10 14 -10 16 ions/cm 2 ; ion energy stream density o0.1 mA/cm 2 ), micromechanical properties of their surface layer (hardness, mechanical modulus and elastic recovery) determined and compared to the virgin materials.
Polimery, 2007
DARIUSZ M. BIELIÑSKI 1)2) *) , CZES£AW OELUSARCZYK 3) , JACEK JAGIELSKI 4)5) , PIOTR LIPIÑSKI 1) Modification of polyethylene by high energy ion or electron beam-structural, micromechanical and conductivity studies of the surface layer Summary-Commercial grade polyethylenes: high density (PE-HD) and ultra-high molecular weight one (PE-UHMW) were subjected to the surface modification by electron beam irradiation (0.6-1.5 MeV/50-500 kGy) and ion beam bombardment (He + 160 keV/2 •10 13-5 •10 16 ions/cm 2 ; Ar + 130 keV/1 •10 13-2 •10 16 ions/cm 2). Effects of modifications were studied by spherical nanoindentation and scratch hardness tests. Contrary to electron beam irradiation, the ion beam bombardment, especially of He + ions, can significantly increase (up to 3 times) hardness of the surface layer of polyethylene in comparison to the bulk. According to Grazing Incidence X-ray Diffraction (GIXRD) it is associated with an increased degree of crystallinity due to the surface modification. Nuclear Reaction Analysis (NRA) reveals a hydrogen release due to ion bombardment which saturates at the CH atomic composition. It cannot however be associated with cross-polymerization or crosslinking of macromolecules because of some unsaturations being present and a graphite formation. Partially graphitized and/or better organized modified macromolecular chains "rooted" in the polymer substrate explain low friction and wear resistance of ion bombarded polyethylenes. Even high stress crackings are not able to proceed with further delamination of the modified surface layer. Treatment of the material with heavy Ar + ions of energy 150-300 keV was combined with an electrical doping by implantation of polyethylene with I + ions of energy 150 keV. Apart an increase in hardness, the modification results additionally in a significant reduction of the surface resistivity (more than 20 times), facilitating a removal of static charge.
Biomedical aspects of ion bombardment of polyethylene
Vacuum, 2009
Press-moulded ultra-high molecular weight polyethylene (UHMWPE) samples were subjected to ion bombardment and effects of the modification studied. Helium, nitrogen, argon and silver ions of energy 65-150 keV and fluences in the range of 1 Â 10 14 to 3 Â 10 16 /cm 2 were applied. The consequences of the modification were studied with FT-IR, Raman and AFM techniques, contact angle measurements, bacteriostaticity and thrombogeneity tests. Surface layer oxidation, graphitization and changes to the surface geometry lead to increase of the surface energy. Modified surface exhibits bacteriostatic properties particularly for higher ion fluences. Aggregation of blood platelets on polymer surface subjected to ion bombardment is limited.
Chemical Changes Created by High Energy Ions in Polyethylene
IEEE Transactions on Electrical Insulation, 1987
Argon and oxygen ions were accelerated with energies of 50 to 150 keV and rastered across high density polyethylene. The free radicals formed in the ion-implanted polyethylene were studied using an electron spin resonance spectrometer. The free radicals formed were stable in air and even survived solvent separation of the undamaged polymer from the ion damaged polymer. Chemical characterizations indicated that pregraphitic or graphitic-like particles are formed with defect sites which are, in effect, free radicals stabilized by a polyaromatic system.
Structural and chemical changes in He+ bombarded polymers and related performance properties
Journal of Applied Physics
The paper presents the effect of He+ ion irradiation of selected polymeric materials: poly(tetrafloroethylene), poly(vinyl chloride), ethylene-propylene-diene monomer rubber, nitrile-butadiene rubber, styrene-butadiene rubber, and natural rubber, on their chemical composition, physical structure, and surface topography. The modification was studied by scanning electron microscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, and differential scanning calorimetry. Irradiation with a high-energy ion beam leads to the release of significant amounts of hydrogen from the surface layer, resulting in an increase in cross-linking that manifests itself by shrinkage of the surface layer, which in turn causes significant stresses leading to the formation of a crack pattern on the polymer surface. The development of microroughness is combined with oxidation. Shallow range of the ions makes the modified layer “anchored” in the substrate via bulk macromolecules, assuring its good ...
Nano-Mechanical Properties of Surface Layers of Polyethylene Modified by Irradiation
Materials, 2020
This study’s goal was to describe the influence of a wide range of ionizing beta radiation upon the changes in surface layer mechanical properties and structural modifications of selected types of polymer. Radiation crosslinking is a process whereby the impingement of high-energy electrons adjusts test sample structures, thus enhancing the useful properties of the material, e.g., hardness, wear-resistance, and creep, in order that they may function properly during their technical use. The selected polymers tested were polyolefin polymers like polyethylene (Low-density polyethylene LDPE, High-density polyethylene HDPE). These samples underwent exposure to electron radiation of differing dosages (33, 66, 99, 132, 165, and 198 kGy). After the crosslinking process, the samples underwent testing of the nano-mechanical properties of their surface layers. This was done by means of a state-of-the-art indentation technique, i.e., depth-sensing indentation (DSI), which detects the immediate c...
Polymer modifications due to absorption of different ionizating radiations
In the last years, an useful collaboration developed between the material engineers and the physicians of Messina University. The study of the intimate structure of a material, before and after its modification induced by an external ionizing radiation source (electrons, ions, gamma) requires the simultaneous presence of specialist in Chemistry, Physics and Engineering in order to define the best modification conditions and the consequent features of the new synthesized material. In particular the polyethylene, employed in different fields, such as microelectronics and biomedicine, was chosen as an important target to modify its properties through ions and electron beam irradiations. Ion beams, with energy of the order of some hundred keV and doses of the order of 10 14 /cm 2 , are able to improve the polyethylene surface properties without change the pristine bulk. Instead, electron beams with energy of about 5 MeV and high dose, improve significantly bulk properties of the polymer. The effects of the ion and electron modifications were investigated with several physics characterization methods, as will be discussed in the following.