Mixed-state wetting and wetting transitions on laser surface engineered polymeric materials

Currently, there is a significant amount of work in the field of wettability science to try and better understand wetting transitions and subsequent developments of mixed-state wetting regimes. This is of extreme importance as this knowledge will have significant impact in those industries and academic fields which rely heavily on adhesion science. This work details the implementation of CO₂ lasers to surface engineer polymeric materials, poly(methyl methacrylate) (PMMA) and polyamide 6,6 (nylon 6,6), to bring about and gain a further understanding of the development of mixed-state wetting regimes. With the laser, the surface roughness (Ra) was dramatically increased by up to 4.5 µm in comparison to the as-received sample (AR). It was determined for all samples that the polar component had a strong inverse relationship with the contact angle, θ. For the laser surface engineered polymers a modest increase in θ indicated the likely formation of a mixed-state wetting regime and highlighted the significant influence of laser-modified surface topography on θ. The polar component and surface pattern were found to be the most dominant parameters governing the wettability characteristics of the laser-surface-modified polymeric materials. The latest state-of-the-art knowledge and understanding of wetting transitions and mixed-state wetting regimes with specific regard to roughened laser surface engineered polymeric materials is discussed identifying significant wettability knowledge and theories.