Soft polyurethanes treated by plasma immersion ion implantation: Structural and mechanical properties of the surface‐modified layer

Abstract

The surfaces of soft polyurethanes (with elastic moduli of 7 and 50 MPa) treated by plasma immersion ion implantation were studied; the materials became hard and wrinkled. The characteristics of the modified surface (modulus, roughness, wave and fractal parameters, linear deformation) and the cross‐sectioned layer were studied in relation to the treatment regime and the modulus of the polymer. A hypothesis that the wrinkling was solely caused by thermal expansion was checked but rejected. The cross‐section of the treated material had a hard part of a certain thickness and a transition zone. The elastic modulus of the hard part was estimated by the finite element method. A comparison of the obtained thicknesses with calculations by TRIM software indicated that the latter gave underestimated results. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 45983.

The Fracture of Plasma-Treated Polyurethane Surface under Fatigue Loading

“…Detailed analysis of structural-mechanical properties of the treated surfaces (roughness, fractal and wave properties, elastic modulus) and the cross-sections of the modified layer are given in the work [19]. In particular, the elastic modulus of the surface, determined by the AFM nanoindentation, increases with the plasma energy and fluence and was 20 MPa for the untreated PU, 125 MPa (PIII 1-16), 254 MPa (1-17) and 1900 MPa (3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17).…”

“…As a result of ion implantation, a hard layer is formed on the surface of the material. Its thickness was estimated experimentally: 25, 30 and 50 nm [19].…”

“…Some portion of the material was then removed from the side surface of the sample by the cryo-ultramicrotome (Leica UC7, Vienna, Austria) at −100 • C using a diamond knife. By this way, the surface containing the cross-section of modified layer in the middle was prepared and its thickness was measured by the AFM [19].…”

“…The real conditions for exploitation of elastomeric implants imply the presence of large cyclic deformations. The stiffness of the plasma-modified layer could be many times greater than the elastic modulus of the soft polymer "substrate" [19]. As a result, even simple uniaxial deformations fracture the modified surface [17,20] and could damage of implant and body tissues.…”

The Fracture of Plasma-Treated Polyurethane Surface under Fatigue Loading

“…The real conditions for exploitation of elastomeric implants imply the presence of large cyclic deformations. The stiffness of the plasma-modified layer is in many times greater than the elastic modulus of the soft polymer "substrate" [19]. As a result, even simple uniaxial deformations lead to fracture of modified surface [18] and could damage of implant and body tissues.…”