Scientists have developed a novel process that converts lignin—a substance that paper manufacturers typically burn or throw away—into high-performance pressure-sensitive adhesives (PSAs). How? They developed a robust synthesis method. It produces intermediate chemicals from raw non-food biomass, such as poplar wood. The chemicals are then converted into high-performance PSAs. The work was done by the Catalysis Center for Energy Innovation (CCEI), an Energy Frontier Research Center at the University of Delaware.
These biomass-derived PSAs exhibited properties that rival those of PSAs produced from petroleum. Currently, PSAs are widely used as the backing that makes cellophane tape sticky. Better still, the properties of these new PSAs can be "tuned" (less sticky or more sticky). The adhesive can be designed simply by modifying the catalyst. Globally, about 80 million tons of lignin are generated annually by paper pulping industries and cellulosic biorefineries. The majority of this lignin is burned for heat. It has a value of about $50/ton. CCEI's method of turning lignin into PSAs—with comparable products selling for about $2000/ton—could enhance the economic viability of biorefineries and have significant societal benefits.
Scientists developed a new and robust process that converts components of lignocellulosic biomass into high-performance high-value PSAs that have properties that rival PSAs produced from petroleum feedstocks. These new polymeric PSAs exhibit high glass transition temperatures, robust thermal stabilities, excellent adhesion, and mechanical properties that may allow them to serve as renewable replacements for existing PSAs. The researchers first developed a robust method to produce functional phenols by depolymerizing the lignin via selective hydrogenolysis using a commercial ruthenium-based catalyst in methanol. Scientists then purified the two main products (4-propylsyringol and 4-propylguaiacol) from the catalyst and the reaction mixture by an inexpensive solvent extraction method. The purified 4-propylsyringol and 4-propylguaiacol were reacted with either acrylate or methacrylate, and the functionalized derivatives were then polymerized by a scalable reversible addition?fragmentation chain-transfer process into this new class of adhesive materials.
Catalysis Center for Energy Innovation and University of Delaware
Vlachos@udel.edu; (302) 831-2830
The polymer synthesis and characterization work was supported financially by the National Science Foundation. The biomass deconstruction and monomer production work was supported financially by the Catalysis Center for Energy Innovation, an Energy Frontier Research Center funded by the Department of Energy, Office of Science, Office of Basic Energy Sciences. The University of Delaware nuclear magnetic resonance facility and RSA-G2 instrument were supported by the Delaware Center of Biomedical Research Excellence program with a grant from National Institutes of Health.
S. Wang, L. Shuai, B. Saha, D.G. Vlachos, and T.H. Epps, "From tree to tape: Direct synthesis of pressure sensitive adhesives from depolymerized raw lignocellulosic biomass". ACS Central Science 4, 701 (2018). [DOI: 10.1021/acscentsci.8b00140]
Catalysis Center for Energy Innovation homepage: www.ccei.udel.edu
Delaware Energy Institute homepage: www.dei.udel.edu