Ancient insect resin could replace synthetic wood glues, study finds
Shellac, a natural resin from lac insects, performs as well as conventional adhesives for woodworking when properly heat-treated, researchers report. The finding could reshape the $10 billion adhesives market and offer furniture and construction companies a biodegradable alternative that meets existing safety standards.
Originaltitel: Shellac as a renewable bio-based adhesive for wood bonding: Toward cleaner and sustainable material solutions
<p>Shellac, a natural resin secreted by the lac insect (Kerria lacca), is a renewable and biodegradable alternative to synthetic adhesives. Although historically used as a coating material, its potential as a wood adhesive under modern standards remains largely unexplored. This study systematically evaluated shellac-based adhesives for bonding European beech (Fagus sylvatica L.), combining standardised performance testing (European Standards EN 204 and EN205) with advanced thermal and chemical characterisation. Overall, six shellac types were assessed under cold- and hot-pressing conditions, and the influence of thermal curing on adhesive properties was investigated using FTIR, DSC, and TGA. Results confirmed that thermal treatment induced polycondensation, forming a crosslinked polyester network that enhanced thermal stability and moisture resistance. The glass transition temperature increased from 42 °C in native shellac to 77–90 °C after curing, while TGA revealed improved thermal stability, with minimal mass loss noted at 200 °C. Bond strength development was modelled using the Hill and Logistic models, respectively, with the Hill model providing a superior fit (R2 = 0.971). Hot-pressing at 200 °C reduced pressing time and improved water resistance. Beyond the determined technical performance, shellac offers sustainability benefits: it is renewable, non-toxic, being produced through low impact processes, capable of supporting rural livelihoods, and aligns with multiple UN Sustainable Development Goals (SDGs). These findings position shellac as a promising bio-based adhesive for niche wood bonding applications, contributing to cleaner production and reduced reliance on petrochemical resins.</p>