Adhesive loses its stick with heat

Jessica Gorman

Like the sticky stuff on Post-It notes, a new epoxy adhesive can bind and unbind materials repeatedly.

The adhesive is the first epoxy that's sticky enough to hold materials together at low temperatures but that reversibly loses its grip when hot, says Jim Aubert, whose team developed the epoxy at Sandia National Laboratories in Albuquerque. Some polymers also show this trait in reverse (SN: 8/21/99, p. 118: http://www.sciencenews.org/pages/sn_arc99/8_21_99/fob6.htm).

Engineers could benefit from a reversible adhesive when building complicated machinery or weapons that might later need updating with new parts or electronics, Aubert suggests. Such an adhesive would also make it easier to fix a problem discovered when a product is assembled or tested or when a machine is dismantled for recycling, he says.

The new epoxy is adhesive between room temperature (about 25°C) and 60°C, but it melts around 90°C to 130°C, says Aubert.

Aubert's team created the easily removable adhesive using conventional epoxy-making materials but added a twist: They built in so-called Diels-Alder bonds, which are common chemical linkages that break at high temperatures.

The epoxy does have two limitations, notes Aubert. It can't bind parts in high-temperature environments such as automotive engines and it loses its reversible bonding capability after about a half-dozen cycles of bonding and releasing.

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References:

2001. Sandia-developed removable adhesive bonds and detaches with temperature changes. Sandia National Laboratories news release. Sept. 25. Available at http://www.sandia.gov/media/NewsRel/NR2001/adhesive.htm.

Further Readings:

Wu, C. 1999. Warmth switches on a polymer's tackiness. Science News 156(Aug. 21):118. Available at http://www.sciencenews.org/pages/sn_arc99/8_21_99/fob6.htm.

Sources:

Jim Aubert
Sandia National Laboratories
P.O. Box 5800
Albuquerque, NM 87185-0888

From Science News, Volume 160, No. 15, October 13, 2001, p. 237.