Temperature indicating device

A device for indicating if an object is exposed to a critical temperature;

• the indicating device comprising:
• (a) a microporous membrane;
• (b) an indicating composition containing less than about 1 wt-% water;
• the composition comprising:
• (i) at least about 50 wt-% of a primary organic component comprising at least one compound that has a freezing point above the critical temperature and does not spontaneously wet out the microporous membrane at a temperature at least about 30.degree. C. above the critical temperature;
• (ii) no greater than about 40 wt-% of a modifying component comprising at least one compound that has a freezing point below the critical temperature and modifies the temperature at which the primary organic component solidifies;
• and
• (iii) no greater than about 20 wt-% of a wetting component comprising at least one compound that has a freezing point below the critical temperature and is capable of spontaneously wetting out the microporous membrane at about the critical temperature;
• and
• (c) means for containing the microporous membrane and the indicating composition;
• wherein the primary organic component, modifying component, and wetting component are miscible liquids above the critical temperature, and are present in a ratio such that the composition does not spontaneously wet out the microporous membrane at a temperature at least about 30.degree. C. above the critical temperature, but does spontaneously wet it out at about the critical temperature upon solidification of a portion of the composition.

A device for indicating if an object is exposed to a critical temperature;

• the indicating device comprising:
• (a) a microporous membrane comprising a polyolefin;
• (b) an indicating composition containing less than about 1 wt-% water;
• the composition comprising:
• (i) at least about 50 wt-% of a primary organic component comprising at least one polyfunctional alcohol that has a freezing point above the critical temperature and does not spontaneously wet out the microporous membrane at a temperature at least about 30.degree. C. above the critical temperature;
• (ii) no greater than about 40 wt-% of a modifying component comprising at least one polyfunctional alcohol that has a freezing point below the critical temperature and modifies the temperature at which the primary organic component solidifies;
• and
• (iii) no greater than about 20 wt-% of a wetting component comprising at least one compound selected from the group consisting of alcohols, ketones, ethers, alkanes, alkenes, amines, and combinations thereof;
• wherein the compound has a freezing point below the critical temperature and is capable of spontaneously wetting out the microporous membrane at about the critical temperature;
• and
• (c) means for containing the microporous membrane and the indicating composition and retarding the transmission of water vapor into the indicating composition;
• wherein the primary organic component, modifying component, and wetting component are miscible liquids above the critical temperature, and are present in a ratio such that the composition does not spontaneously wet out the microporous membrane at a temperature at least about 30.degree. C. above the critical temperature, but does spontaneously wet it out at about the critical temperature upon solidification of a portion of the composition.