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Fluorine Plasma Treatments of Poly(propylene) Films, 2 – Modeling Reaction Mechanisms and Scaling
Author(s) -
Yang Yang,
Strobel Mark,
Kirk Seth,
Kushner Mark J.
Publication year - 2010
Publication title -
plasma processes and polymers
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.644
H-Index - 74
eISSN - 1612-8869
pISSN - 1612-8850
DOI - 10.1002/ppap.200900114
Subject(s) - passivation , fluorine , surface modification , hydrocarbon , plasma , radical , ion , materials science , alkyl , steric effects , polymer , photochemistry , chemical engineering , chemistry , organic chemistry , nanotechnology , layer (electronics) , composite material , physics , quantum mechanics , engineering
The surface properties of commodity hydrocarbon polymers such as poly(propylene) (PP) can be modified by functionalization with plasma‐generated radicals and ions. For example, affixing fluorine to a hydrocarbon surface lowers surface energy and increases hydrophobicity. One such process is treatment of PP films in low‐pressure, capacitively coupled plasmas (CCPs) sustained in F 2 ‐containing gas mixtures. F atoms produced in the plasma abstract H atoms from the hydrocarbon and passivate the resulting alkyl sites producing CF n sites. Energetic ion and photon fluxes sputter and initiate crosslinking. In this paper, the plasma fluorination of PP in a CCP sustained in Ar/F 2 is discussed with results from a two‐dimensional plasma hydrodynamics model. The surface reaction mechanism includes a hierarchy of H abstraction and F/F 2 passivation reactions, as well as crosslinking, and ion and photon‐activated processes. Predictions for surface composition were compared to experiments. We found that the lack of total fluorination with long plasma exposure is likely caused by crosslinking, which creates CC bonds that might otherwise be passivated by F atoms. Increasing steric hindrances as fluorination proceeds also contribute to lower F/C ratios.