Effect of Beta Radiation on the Quality of the Bonded Joint for Difficult to Bond Polyolefins.

David Manas,Pavel Stoklasek,Martin Ovsik,Miroslav Manas,Ales Mizera,Martin Bednarik

doi:10.3390/polym11111863

Abstract

Bonding is increasingly being used, and it is an ever-evolving method for creating unbreakable bonds. The strength of adhesive bonds determines, to a significant extent, the possible applications of this technology and is influenced by many factors. In addition to the type of adhesive used, the characteristics of the surface layers play a significant role; therefore, significant attention is paid to their adjustment and modification. Radiation crosslinking is one of the most important methods for modifying polymer properties. Currently, the most frequently used type of radiation for polymer crosslinking is beta minus (β−) radiation, which affects not only mechanical but also surface properties, chemical and temperature resistance, and surface layer characteristics of polymers. This study investigated the effect of β− radiation on the surface layer properties of low-density polyethylene (LDPE), high-density polyethylene (HDPE), and polypropylene (PP) and the effects of surface-layer modification on the ultimate tensile strength of bonded joints. Based on the results, we concluded that β− radiation significantly changes the properties of the tested surface layers, increases the surface energy, and improves the adhesiveness of bonds. Consequently, the final strength of the LDPE, HDPE, and PP bonds increases significantly.

Highlights

Nowadays, polymer materials are used for a wide range of industrial applications and a wide variety of purposes, including packaging materials, household products, and sports products, as well as for very demanding applications in healthcare, the automotive, aerospace, electrotechnics, and electronics industries
This study focused on the influence of irradiation on the properties of surface layers, such as the wetting contact angle, free surface energy, and adhesiveness, of selected types of polyolefin polymeric materials, and built on the work of Bednarik et al [33,34,35,36,37]
The high-density polyethylene (HDPE), low-density polyethylene (LDPE), and PP polyolefin materials were selected for their bonding difficulties

Summary

Introduction

Polymer materials are used for a wide range of industrial applications and a wide variety of purposes, including packaging materials, household products, and sports products, as well as for very demanding applications in healthcare, the automotive, aerospace, electrotechnics, and electronics industries. Welding and bonding technologies are used to create non-dismountable bonds. The ability to form sufficiently rigid bonds depends on the adhesive used and surface-layer properties of the bonded materials, and, in particular, for polymeric materials, it is necessary to modify the surfaces of the adhered components. Modifying the surface layers allows the creation of controlled interfaces, which could be used to achieve desired properties, such as compatibility and adhesiveness [1,2]. The surface energies of polymers are lower than those of metals, and polymers tend to form very poor-quality adhesive bonds. A variety of methods are used to treat polymer-material surfaces, Polymers 2019, 11, 1863; doi:10.3390/polym11111863 www.mdpi.com/journal/polymers

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