ABSTRACT
The 3M Monitor Mark (3M Co., St. Paul, Minnesota,
U.S.A.) is based on diffusion of proprietary polymer mate-
rials. A viscoelastic material migrates into a diffusely light-
reflective porous matrix at a temperature dependent rate.
This causes a progressive change of the light transmissivity
of the porous matrix and provides a visual response. The
TTI is activated by adhesion of the two materials that
before use can be stored separately for a long period at
ambient temperature.
