Surface Laser Micropatterning of Polyethylene (PE) to Increase the Shearing Strength of Adhesive Joints

Abstract

In the introduction, we present an overview of previous research on this subject in order to help the reader review possible technological solutions regarding the joining of construction materials. The original research presented in this article concerns the results of increasing the shear strength of adhesive joints of plastics using various types of surface preparation (laser texturing). Laser texturing consists in developing the surface by applying various geometric patterns of appropriate shapes and depths, as well as its density on the surface. The above parameters are currently selected in an empirical way as research is still being developed as part of a research project. The textures obtained in this way are subjected to microscopic examination. Then, a layer of glue is applied, and the samples prepared in this way, after drying, are subjected to various destructive tests, e.g., tensile, shear, and bending. In this article, we attempted to test the strength of the bonded joint of polyethylene (PE). The impact of a laser beam with ultrashort picosecond pulses was used in the research. Tools in the form of a TRUMPF TruMicro 5325c device integrated with a SCANLAB GALVO scanning head were used. This enabled ablative material removal without the presence of a heat affected zone (HAZ) in the non-laser part. Ultrashort laser pulses remove material without melting the non-exposed area by the laser beam. On the basis of the tests performed (in this article and previous research works of the authors), it was shown that the method increases the shear strength of the glued joints made in the tested construction materials. This is confirmed by laboratory results of tribological tests. The laser treatment parameters used, which are shown in this article, did not lead to the appearance of cracks in the micromachined materials. Research has shown that the connections between elements with a properly selected micropattern are characterized by a several-fold increase in the strength of joints, unlike materials without a micropattern. The presented method may be helpful for use as a technology for joining plastics.

Keywords

• UV laser
• picosecond laser
• adhesive joints
• micromachining
• micropatterning
• polyethylene (PE)