Plasma polymer film as a model interlayer for polymer composites

In this paper, a plasma-enhanced chemical vapor deposition process that is useful for the preparation of thin and ultrathin films of controlled mechanical properties is identified. Plasma-polymerized films of vinyltriethoxysilane were deposited on planar substrates and analyzed using nanoindentation measurements of the Young's modulus of the films, adhesion bonding at the film/glass interface, chemical composition, and structure. The modulus of the plasma polymer film can be controlled simply by the effective power fed into the capacitive-coupled low-pressure plasma. The single film was tested as an interlayer in glass fiber (GF)/polyester composites. GF bundles were surface modified by plasma polymer in a unique technological system, enabling continuous processing of the bundle. GF/polyester composites in the form of short beams were manufactured using the coated fibers and tested according to the standard test method. By increasing the interlayer modulus, the short-beam strength was enhanced up to 112% compared with the untreated GFs, and this enhancement was also supported by an improvement in interfacial bonding.