Forest Service Continues To Make a Better Postage Stamp
The U.S. Postal Service has sponsored cooperative research projects at the Forest Products Laboratory for more than 20 years. Initial research developed stamp adhesives that do not cause problems during paper recycling. More recently, the cooperation moved to accelerated aging tests for stamps and development of compostable adhesives.
Researchers are developing improved performance and accelerated aging tests to assure that Forever Stamps are indeed useful—if not forever—at least close enough to qualify for the name. The electron micrograph shows a piece of the silicone-release liner stuck to a pressure sensitive adhesive (PSA) on the back of an experimental stamp that has been subjected to an accelerated aging process. Normally the laminate separates between the silicone and adhesive leaving a clean adhesive surface ready to attach to an envelope. The silicone contamination could ultimately cause the stamp to fall off during mail processing. Catching problems like this before stamps are released illustrates the importance of this research.
In an effort to reduce the environmental effect of stamp materials, researchers are developing new PSAs that are produced from renewable materials and that will degrade in landfills. The current approach is to produce PSAs using pendent polylactic acid macromers attached to polymer backbones, which allows for biodegradation but still provides good performance. Beyond developing adhesives that may be used on future stamps and other commercial products, researchers are developing experimental methods for determining the biodegradation rate of new materials.
Forest Service Partners