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In this study, nitrogen plasma treatment at atmospheric pressure was used to modify the surface of poiylactic acid (PLA). especially /V.Î low surface energy and wettahility. which do not favor the interface adhesion with another material when blended. The dielectric hairier discharge (DBD) configuration was selected. Treatment time was varied, and induced chemical and topographical surface modifications were assessed. Attention was first focused on the effect of the treatment duration on the hydrophilicity and the topography of PLA. Results showed that plasma treatment enhanced the PLA surface hydrophilicity. The overall suiface roughness was also found to he increased. Moreover, both properties rose with increasing treatment time. Thus, according to the Wenzel's relation, the surface roughening contributed to the enhancement of the PLA hydrophilicity generated by plasma treatment. Then, the chemical surface changes induced by specific plasma activation were studied. Analyses pointed out the incorporation of hydrophilic groups such as nitrogen functional species after treatment. The stability of this treatment under air was also investigated: measurements showed that the hydrophobic recovery mainly occurred the first hours of storage.

In this paper, the effect of water on the friction and wear of a carbon fiber reinforced epoxy tested under reciprocating sliding against a stainless steel counter body is reported. The tribological behavior of unidirectional carbon fiber reinforced epoxy composite was investigated in ambient air and in demineralized water, and the role of water on the (sub-) surface degradation is discussed. The effect of sliding direction relative to the fiber orientation has been studied. The correlation between the debonding of carbon fibers at the fiber-epoxy interface, and the wear behavior of the carbon fiber composite are discussed based on an indepth analysis of the worn surfaces done by environmental scanning electron microscopy, white light interferometry, atomic force microscopy, and focused ion beam. We demonstrate that the carbon fiber reinforcement greatly improves the tribological properties of epoxy under sliding in both dry environment and demineralized water. A reciprocating sliding performed along an anti-parallel direction to the fiber orientation under dry conditions results in a large degradation by debonding and breaking of the carbon fibers compared to sliding in 2 parallel and perpendicular directions. Immersion in water has a harmful effect on the wear resistance of the carbon fiber reinforced epoxy composite. The competition between crack growth and the wear rate of epoxy matrix and/or carbon fibers in the sliding track determines the level of material loss of the composite in both test environments.