Page 75 - Handbook of Adhesion Promoters

68 Substrates - Surface Condition and Treat-

Figure 4.15. Topography of the surface of poly(lactic acid) films (a) before and (b) after corona treatment.
[Adapted, by permission, from Izdebska, J, Corona Treatment. Printing on Polymers, WilliamAndrew, 2016,
pp. 123-42.]
The electric discharge machining process was applied for Ti–6Al–4V alloy for
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potential application in orthopedics. The process induced the surface macro-roughness
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and chemical changes to the surface. The treated alloy provided better substrate for the
adhesion and growth of human bone-derived cells than the alloy plasma-sprayed with
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TiO . The electric discharge machining-treated Ti-6Al-4V alloy is a promising material
2
for the construction of bone implants, in particular implants which require firm and quick
integration with the surrounding bone tissue, such as bone-anchoring parts of joint pros-
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theses.
4.2.7 LASER
The modifications induced on PET by an excimer laser irradiation performed below the
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polymer ablation threshold improved the aluminum/PET adhesion. Excimer laser at 193
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or 248 nm was used. The treatments were carried out at atmospheric pressure in air,
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under helium, or He-O (5%) atmospheres.
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Stainless steel was micro/nanostructured through femtosecond laser treatment. The
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process resulted in an increase in hydrophobicity and carbon content of the surface. The
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process increased in vitro bone formation rate. A significant improvement in adhesion of
human endothelial cells and human bone marrow mesenchymal stem cells, the cells
involved in microvessel and bone formation, respectively, and a significant decrease in
fibroblast adhesion, which is implicated in osteolysis and aseptic loosening of prostheses
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resulted from laser treatment.
For surfaces irradiated by ArF laser below the ablation threshold, a high reduction in
the number of the adhered platelets was observed; while their number increased in sam-
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ples treated at the fluence above the ablation threshold. The change in platelet adhesion
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was attributed to the changes in chemistry and roughness.
A high power diode laser was used to improve the wettability and adhesion charac-
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teristics of ceramic materials. The treatment resulted in a decrease of the contact angles
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of ceramic materials.
An excimer laser treatment (193 or 248 nm) was adapted as a means to control the
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adhesion of glass/epoxy and carbon/epoxy composites. Figure 4.16 shows that the num-
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ber of laser pulses increases surface roughness and polymer layer ablation. The highest
ablation mode is responsible for a fairly high roughness value (S =17.2 µm), which is
a
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more than 20 times the value of the untreated sample. At 1-3 pulses, only the surface
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cleaning occurs. Above four pulses, the ablation takes place with the resulting chemical