Adhesive Force Improvement of Polyethylene Terephthalate (PET)/Epoxy Resin Joint by Electron Beam to PET Prior to Assembly

Adhesive 2-layer lamination joints of polyethylene terephthalate (PET)/epoxy resin were prepared without the use of hot press using a new adhesion method of applying homogeneous low energy electron beam irradiation (HLEBI) to the PET prior to assembly by hand pressure. HLEBI treatment within the range of 0.13 to 0.43 MGy increased the adhesive force of peeling (degrees F-p) substantially over the untreated. The largest degrees F-p values at optimal dose 0.30 MGy were 12.4, 37.2 and 190Nm(-1), which were more than 2.2, 2.8 and 9.5 times larger than 5.76, 13.5 and 20.0NM(-1) of the untreated at low-, median- and high peeling force accumulative probability, P-p of 0.06, 0.50 and 0.94, respectively. The statistically lowest degrees F-p for safety design (F-s at P-p = 0) iterated by the 3-parameter Weibull equation was raised from zero for the untreated to 10.7 Nm(-1) for the 0.30 MGy samples indicating increased reliability by the HLEBI. XPS (X-Ray Photoelectron Spectroscopy) observations of the peeled 0.30 MGy HLEBI PET revealed generation of a C-O peak at 286 eV possibly explaining the increased adhesion. Therefore residual epoxy deposition is apparently found to be retained on the PET sheet by inter-matrix fracture of epoxy resin further into the thickness. This can be explained by the adhesion force from crosslinking between PET/epoxy being stronger than the cohesive force of epoxy polymer itself. Since the experimental data shows the optimum HLEBI dose is about 0.30 MGy, above which at 0.43 MGy the degrees F-p begins to drop, carefulness in optimization is highly recommended when applying in industry to insure safety.