What are pressure-sensitive adhesives?
Pressure-sensitive adhesives (PSA), also known as “self-adhesives”, are the adhesives used for the peel-and-stick variety of labels, stamps, “sticky notes,” tape, etc. that are so popular today. PSAs do not require any moisture to activate them, unlike moisture-activated adhesives still used for most envelope closures.
Are pressure-sensitive adhesives a problem for recycling?
There are “recycling-compatible” PSA’s” available on the market which are not problematic for recycling. However, other PSA products do cause problems for paper recycling systems that use water as the medium to transform recovered paper into “pulp.” PSAs that are not recycling-compatible do not dissolve in water, but rather fragment into smaller particles during the repulping process. These particles—known as “stickies”—deform under heat and pressure, making them difficult to screen or filter out of the pulp. Stickies can become lodged on papermaking equipment or even in the paper itself, often causing serious damage to both. Consequently, non-recycling compatible PSAs exact a considerable cost on the paper recycling industry, both in direct costs to paper mills and in reduced prices received by recovered paper collectors and processors.
The U.S. Postal Service (USPS) is a major user of PSA-based products, accounting for about 14 percent of U.S. consumption. In response to concerns about the recyclability of PSAs, the USPS led a multi-disciplinary effort that successfully developed a recycling-compatible adhesive (RCA). The USPS now uses RCA’s exclusively in stamps, and other manufacturers of PSA products have lines of products which use RCA’s. However, each company uses different terminology such as “recycling-compatible”, “100% recyclable”, “water-soluble adhesive”, or “environmentally benign” for their RCA’s. When purchasing PSAs make sure to inquire with the manufacturer to verify that the PSA is a RCA.
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