Selective Surface Modification of Polypropylene using Underwater Plasma Technique or Underwater Capillary Discharge

Abstract

AbstractAmong new types of plasma processes, the underwater plasma is one of the most attractive methods for functionalization of polymer surfaces. The interesting features of plasma solution system are that the material surfaces to be modified remain in contact with the plasma‐moderated solution. The role of plasma‐moderated liquids, allows the reach of the reactive species through solution onto the geometrically hindered sites. The UV radiation produced in plasma formation helps in generating additional excited, ionized, and dissociated molecules and species in the reaction solution. An interesting feature of the technique is its flexibility to use a wide variety of additives as or in solution system. This allows us to create a selective or monotype functionalization of material surfaces. Such system was studied for the selective hydroxyl functionalization of polypropylene surface. The oxidation of polymer surfaces and the introduction of O‐containing functional groups by underwater plasma was found to exceed concentrations typically achieved in oxygen low‐pressure gas discharge plasmas up‐to two‐folds (maximal 56 O/100 C). The fraction of OH groups among all O‐containing moieties amounts from 25 to 40% in comparison to that in the gas plasma of about 10% OH groups. Addition of hydrogen peroxide into this same system increases the fraction of CO bonds up to 75% (27‐OH/100 O). A study was focused to optimize the role of hydrogen peroxide on the efficiency of oxidation and selectivity with chemical derivatization with respect to the formation of mono‐sort hydroxyl functionalities, calculated using a chemical derivatization technique.