Unlike a sharp boundary line, the interphase is a three-dimensional region where the properties of the adhesive gradually transition into the properties of the substrate. This zone includes absorbed adhesive molecules, modified substrate structures, and chemical coupling agents. The strength and durability of a bonded joint depend heavily on the mechanical properties of this blended region.
The plasma treatment deepens the interphase, giving the urethane a much better mechanical lock into the polymer matrix.
Related terms
Mechanical interlock
Adhesion gained by adhesive flowing into pores and roughness and locking in once it hardens.
Adherend
Each of the parts in a bonded joint; the surface the adhesive has to grip.
Primer
A thin first coat wiped or sprayed onto a bonding surface so the adhesive grips better or the fresh prep stays clean.