
11: POLY(NAPHTHALATES) 269
ca. 30% and the barrier properties are markedly
increased.
The permeability can bereduced bya physical vapor
deposition (PVD) process and chemical vapor depo-
sition (CVD). PVD processes operate under reduced
pressure and include evaporation and sputtering, in the
absence of chemical reactions in the gas phase and at
the substrate surface. An overview of PVD processes
shows that CVD processes utilize volatile precursors
that are decomposed by means of heat, photons, or
plasma. Plasma enhanced CVD (PECVD) is applica-
ble for thermally sensitive substrates, such as poly-
mers. It has become the most widely used process for
the deposition ...