IMPROVEMENT OF POLYMER SURFACE LAYER BY ELECTRON RADIATION

AbstractBioactive glasses have attractive characteristics as a scaffold material for healing bone defects but their brittle mechanical response, particularly in bending, is a concern. Recent studies have shown that coating the external surface of strong porous bioactive glass (13-93) scaffolds with an adherent biodegradable polymer layer can significantly improve their load-bearing capacity andwork of fracture, resulting in a non-brittle mechanical response. In the present study, finite element modeling (FEM) was used to analyze the mechanical response in four-point bending of composites composed of a porous glass scaffold and an adherent polymer surface layer. The glass scaffold with a cylindrical geometry (diameter = 4.2 mm; porosity = 20%) was composed of randomly arranged unidirectional fibers (diameter 200-700 μm) thatwere bonded at their contact points. The thickness of the polymer layer was 500 μm. By analyzing the stresses in the individual glass fibers, the simulations can account for the main trends in the observed mechanical response of practical composites with a similar architecture composed of a bioactive glass (13-93) scaffold and an adherent polylactic acid surface layer. These FEM simulations could play a useful role in designing bioactive glass composites with improved mechanical properties.

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Refinement of Nanoporous Copper with Poly(vinyl alcohol) During Dealloying Amorphous Mg65Cu25Y10 Precursors

Journal of Nanoscience and Nanotechnology ◽

10.1166/jnn.2020.17410 ◽

2020 ◽

Vol 20 (6) ◽

pp. 3568-3575

Author(s):

Zhen-Hua Dan ◽

Li-Jun Xu ◽

Yue-Cheng Dong ◽

Ying Wang ◽

Feng-Xiang Qin ◽

...

Keyword(s):

Polymer Surface ◽

Selective Dissolution ◽

Polymerization Process ◽

Poly Vinyl Alcohol ◽

Small Scale ◽

Nanoporous Copper ◽

Reduced Rate ◽

20 Nm ◽

Polymer Surface Layer ◽

Ligament Size

Ultrafine nanoporous copper (UNP Cu) with a characteristic pore size of about 12 nm and a ligament size of about 14 nm was fabricated from amorphous Mg65Cu25Y10 precursor alloys after dealloying in a 0.1 M H2SO4 solution modified by poly(vinyly alcohol) polymers with a molecular weight of 105000 g/mol (PVA-124). The suppression of the surface diffusion from PVA-124 reduced the size of the nanopores and ligaments to 20 nm when the concentration of the added PVA-124 exceeded 0.1 g L−1. When the concentration of the added PVA-124 exceeded 2 g L−1, PVA-124 triggered the polymerization process. The resultant polymer surface layer on the fcc Cu ligaments was shown to reduce the rate of selective dissolution. It was also shown that extending the immersion time resulted in a suppression of coarsening. The introduction of PVA-124 polymer into acids resulted in a higher viscosity of the dealloying solutions, particularly when the concentration of PVA-124 was higher than 1.0 g L−1. This viscosity was shown not only to reduced rate of diffusion of Cu adatoms in PVA-124 solutions, but also forced the accumulation of Cu adatoms to form small scale UNP Cu.

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Polyamide Surface Layer Nano-Indentation and Thermal Properties Modified by Irradiation

Materials ◽

10.3390/ma13132915 ◽

2020 ◽

Vol 13 (13) ◽

pp. 2915 ◽

Cited By ~ 2

Author(s):

Martin Ovsik ◽

Miroslav Manas ◽

Michal Stanek ◽

Adam Dockal ◽

Jiri Vanek ◽

...

Keyword(s):

Mechanical Properties ◽

Surface Layer ◽

Cross Linking ◽

Indentation Hardness ◽

Electron Radiation ◽

Temperature Resistance ◽

Nano Indentation ◽

3D Network ◽

The Creation ◽

The Cross

This study describes the effect of electron radiation on the nano-mechanical properties of surface layers of selected polyamide (PA) types. Electron radiation initiates the cross-linking of macromolecules in the polyamide structure, leading to the creation of a 3D network which fundamentally changes the properties of the tested polymers. Selected types of polyamide (PA 6, PA 66 and PA 9T) were exposed to various intensities of electron radiation (33 kGy, 66 kGy, 99 kGy, 132 kGy, 165 kGy and 198 kGy). The cross-linked polyamides’ surface properties were measured by means of the modern nano-indentation technique (Depth Sensing Indentation; DSI), which operates on the principle of the immediate detection of indenter penetration depth in dependence on the applied load. The evaluation was preformed using the Oliver–Pharr method. The effect of electron radiation on the tested polyamides manifested itself in the creation of a 3D network, which led to an increase of surface layer properties, such as indentation hardness, elastic modulus, creep and temperature resistance, by up to 93%. The increase of temperature and mechanical properties substantially broadens the field of application of these materials in technical practice, especially when higher temperature resistance is required. The positive changes to the nano-mechanical properties as well as mechanical and temperature capabilities instigated by the cross-linking process were confirmed by the gel volume test. These measurements lay the foundation for a detailed study of this topic, as well as for a more effective means of modifying chosen properties of technical polyamide products by radiation.

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