Improved thermal stability of FEP ferroelectrets through inner voids surface modification
Fluoroethylenepropylen (FEP) is one of the most widely used materials for space-charge electrets. The stability of negative homo-charge in this material is among the highest of all non-polar polymers. However, an asymmetry in the charge stability for different polarities restricts the use of FEP electrets in several applications and in particular in layered ferroelectret systems. Polymer modification can be one of the possible approaches to the solution of the problem of positive homo-charge stabilization in FEP. Several different techniques are available for polymer modification. Among them is molecular-layer deposition, an efficient tool for polymer-surface modification. The technique works by embedding nanostructures that contain the desired chemical elements into the surface of the polymer. Hence, it is possible to modify its chemical and physical properties, including its electret behavior. In the present paper, the surface modification of FEP polymer-electret films by means of titanium tetrachloride vapor is therefore investigated.