Page 76 - Handbook of Adhesion Promoters

4.2 Surface treatment 69

Figure 4.16. Surface profilometry and average roughness of glass/epoxy surfaces treated with different excimer
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laser beams conditions: (A) 150 mJ/cm -40 pulses (Sa=0.6 µm). (B) 150 mJ/cm -50 pulses (Sa=3.3 µm). (C)
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150 mJ/cm -400 pulses (Sa=13.1 µm). (D) 500 mJ/cm -500 pulses (Sa=17.2 µm). [Adapted, by permission, from
Bénard, Q; Fois, M; Grisel, M; Laurens, P, Int. J. Adh. Adh., 26, 7, 543-9, 2006.]
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composition remaining the same whatever the parameters used. The use of excimer laser
treatment can efficiently enhance single lap shear performances of composite assem-
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blies. The laser parameters for a given composite material/adhesive system have to be
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optimized in order to obtain the most desirable treatment.
The femtosecond laser treatment (a central wavelength of 1030 nm and a pulse dura-
tion of 500 fs) of titanium enhances the hydrophilicity and the surface free energy of the
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material. The femtosecond laser treatment reduces significantly the adhesion of Staphy-
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lococcus aureus and biofilm formation. Femtosecond laser surface texturing of titanium
is a simple and promising method for endowing dental and orthopedic implants with anti-
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bacterial properties. The nanotopography of the laser-induced textures reduces bacteria
adhesion because the size of individual features and the average distance between them is
such that the penetration of bacteria is inhibited, reducing the area of the contact interface
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between individual bacterium and the metal. Also, bacteria agglomeration is reduced,
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decreasing the tendency to form biofilms.
Polyamide-6 was irradiated by a pulsed ultraviolet excimer laser with a fluence
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below its ablation threshold. The irradiated samples have higher oxygen content than
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control. The carbonyl groups significantly decreased but hydroxyl groups increased after
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low-fluence laser irradiation.
The physicochemical and biological properties of poly(ethylene terephthalate) films,
currently used for medical devices (vascular prostheses) were studied after irradiation
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with excimer laser. The surface energy of PET increased depending on the applied flu-
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ency. The characterization of the surface demonstrated the appearance of new chemical
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species favorable for cell attachment. The laser treatment improved cell proliferation (up
to 140%), vitality (10% higher than controls), morphology and adhesion kinetics (more
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than 16% of control).
A nanosecond pulsed Nd:YAG laser was selected for treatment of PEEK surfaces, to
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increase the performance of lap shear adhesive joints. The strength of adhesively bonded
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joints was greatly improved by laser treatment (up to 13 times). The higher laser power