An aluminum/polycarbonate (Al/PC) joint by homogeneous low voltage electron beam irradiation (HLEBI) to PC prior to lamination assembly and hot-press

Abstract

A 2-layer aluminum/polycarbonate (Al/PC) joint was fabricated between half specimens of typically difficult to adhere Al and PC without use of welding, fasteners, rivets, chemical treatment or glue by a new double-step adhesion method: Applying a low dose of homogeneous low energy electron beam irradiation (HLEBI) to only the PC connecting surface, prior to lamination assembly and hot press at 418 K for 3.0 min under 15 MPa pressure. Experimental results showed 0.30 MGy along with 0.22 MGy had adhesion created in all 11 samples of their data sets [11/11], although data sets of untreated (hot press alone), 0.04, 0.13 and 0.43 MGy had adhesion created in less samples in their data sets at [2/11], [2/11], [6/11] and [10/11], respectively. Moreover, applying the 0.30 MGy HLEBI exhibited the highest mean adhesive force of peeling resistance, Fp over all the data sets, at all peeling probabilities (Pp). Notably, at high-Pp of 0.94 the 0.30 MGy HLEBI raised the °Fp significantly, 1517% from 1.48 of the untreated to 23.95 Nm-1. Based on the 3-parameter Weibull equation, the statistically lowest Fp at Pp= 0 (Fs) from 0.30 MGy-HLEBI was the highest value over all other data sets at 3.10 Nm-1. XPS (X-ray photoelectron spectroscopy) of the peeled Al side revealed a C(1s) peak shift in binding energy from 283.8 eV (C-C) to 284.3 eV (C=C), along with increase in O(1s) C=O peak intensity (531.8 eV) indicating the 0.30 MGy HLEBI generates increased reactive double bond (φ-bond) sites which can explain stronger °Fp of Al/PC joint over the untreated. Since HLEBI cuts the chemical bonds and generates active terminated atoms with dangling bonds in PC polymer, the increased adhesion force in the Al/PC joint can be explained by the chemical bonding at the interface.