Abstract
Processes such as ablation, erosion and corrosion generally create roughness patterns on solid surfaces. Despite the randomness of this phenomenon, some patterns can be described mathematically by studying statistically the mechanisms behind them. This paper reports an experimental study on the temporal evolution of the roughness development of polymer surfaces exposed to argon non-thermal plasma under reduced pressure of 5 mbar and 65 W of applied power. The substrates studied were polypropylene, high density polyethylene, polyamide-6 and poly(ether ether)ketone. The mean roughness data as well as the saturation roughness values showed differences between polyolefin and polymers containing heteroatoms and notably the dependence of the etching on the packing density of the polymer chains. The plasma-etched surfaces were described statistically as self-affine surfaces using scaling law analysis, exhibiting roughness exponents of α ca.0.73 ± 0.2 and growth exponents of β ca. 1.0 ± 0.1. The roughness increases and decreases successively during treatment although presenting a general linear behavior in a non-monotonous way, as a function of time. The models for the shadowing and redistribution of active species can be complemented with the transient crosslinking model of the observed flattening stages.
Highlights
The roughness of an ordinary polymeric surface, natural or synthetic is an important feature that modulates the interactions between the medium and the interface
The composition analysis has been performed on the basis of the intensities of O 1s and C 1s in a standard way, using appropriate atomic sensitivity factors (ASFs)
Based on the properties of the polymers investigated in this study, the crosslinking effect appears to be mainly responsible for the observed rigidity and resistance to bombardment by the species originating from the plasma source
Summary
The roughness of an ordinary polymeric surface, natural or synthetic is an important feature that modulates the interactions between the medium and the interface. Increasing the roughness of a surface or inducing the surface roughness development or growth in the form of electrochemical deposition, erosion, corrosion or the growth of films or crystals, may result in different flat, facetted, pointed or disordered forms and complex structures.[2] estimating the roughness of a surface and the surface energy is the key to understanding surface phenomena, in general, in terms of its application, a surface These processes and the growth phenomena are studied using statistical mechanics, which is used to develop and explain macroscopic and mesoscopic laws for microscopic systems.[7] Since the properties of a thin-film are related to its microstructure, especially to its morphology and surface roughness,[8] the growth of a thin-film surface, or surface growth can be evaluated by a dynamical study. The non-thermal plasma (NTP) treatment can change physical and/or chemical properties of solid surfaces, which is useful in several technological areas such as subtractive microfabrication, photolithography, superhydrophilic surfaces, adhesion promotion, friction coefficient and coating processes with the deposition of active or protective
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