Synthesis by plasma-enhanced chemical-vapor deposition and characterization of siliconlike films with hydrophobic functionalities for improved long-term geometric stability of fiber-reinforced polymers

Amorphous siliconlike films with hydrophobic functionalities have been deposited by plasma-enhanced chemical-vapor deposition on carbon-fiber-reinforced polymer (CFRP) unidirectional laminates used for micromechanical applications where high strength-to-weight and high stiffness-to-weight ratios are required. To improve long-term geometrical stability in ultrahigh-precision machine structures, hydrophobic CFRP materials are desirable. Three layers have been grown with different plasma-process parameters from a mixture of hexamethyldisiloxane, O-2 and Ar. Chemical composition, water contact angle, surface energy, morphology, and tribological properties have been evaluated to choose the one that best fulfills hydrophobicity, wear, and scratch resistance. Wear tests have also been carried out on CFRP laminates coated with a polyurethane layer to compare the wear performance of the above specimens with that of a conventional hydrophobic coating. Scanning electron microscope images show a very good adhesion of the films to the composite substrate because the failure of the film and of the substrate (such as fiber failure) take place simultaneously.