Nano-Mechanical Properties of Surface Layers of Polyethylene Modified by Irradiation.

Martin Ovsik,Adam Dockal,Ales Mizera,Milan Adamek,Michal Stanek,Martin Bednarik,Miroslav Manas,Petr Fluxa

doi:10.3390/ma13040929

Abstract

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 change in the indentation depth associated with the applied force. Indeed, the results indicated that the optimal radiation dosage increased the mechanical properties by up to 57%; however, the beneficial levels of radiation varied with each material. Furthermore, these modifications faced examination from the structural perspective. For this purpose, a gel test, Raman spectroscopy, and crystalline portion determination by X-ray all confirmed the assumed trends.

Highlights

The research papers and literature cited in this study have focused on description of the influence of ionizing radiation on the tested polymers’ properties
This research dealt, in particular, with the study of nano-mechanical property modifications in low-density polyethylene (LDPE) and high-density polyethylene (HDPE) induced by radiation crosslinking
One desired effect is to add some properties of high-tech polymers into standard and construction polymers by crosslinking, which can be achieved by irradiation, replacing expensive materials in many applications

Summary

Introduction

The research papers and literature cited in this study have focused on description of the influence of ionizing radiation on the tested polymers’ properties. These sources are, insufficient, since they do not contain the required amount of complex information. Relevant information about the correlation between ionizing beta radiation and morphology development is lacking This means that the exact modification of a polymer’s mechanical properties by radiation crosslinking for industrial applications is quite challenging. If one of the groups is multifunctional, swelling and elongation with branching is observable. This leads to the creation of an infinite 3D network (Figure 1), i.e., a gel

Methods

Results

Conclusion