Technology advancements continue to be made in the development of resin adhesives from renewable resources. The alkaline-digested aqueous products of biomass from peanut hulls, pine barks, and pecan shell flour have been successfully used to replace up to 80% of the phenol in phenolic resins. Furthermore, these fast-cure copolymer resins
can be made into room temperature laminating adhesives by grafting with less than 10% of resorcinol.
Although the wattle tannins wood adhesives have been commercially produced since 1971, a finger joint adhesives have been developed with southern pine bark tannin that replaced 50% of the PRF resin in honeymoon system. With simple pH adjustment in gluemix to control the reactivity, a non-fortified tannin extracts have been developed to provide an excellent bonding quality of particleboard at industrial production schedules.
Various lignins have been evaluated as substitute of up to 50% of the PF resin solids used for adhesives in plywood and OSB. Lignins are also used with UF resins as formaldehyde scavengers and improve glueline quality. The addition of polymeric MDI increased the cross-linkage of methylolated kraft lignin and improved glue bond.
Carbohydrates have been reacted with phenol and/or urea to form thermosetting exterior adhesives. Resorcinol grafted carbohydrate-phenol resins were used to bond high moisture content veneer under a hot press and to laminate glulam under cold setting. Excellent glueline quality was obtained from starch copolymer resins by reacting maltodextrin with PF prepolymer.
Lignocellulosic materials with esterification or methylation have been liquefied under elevated temperatures in organic solvent. After neutralization with NaOH, the products were reacted with formalin to form resol resin wood adhesive. Most recently, the phenolic compounds extracting from pyrolysis biomass oil have also been successfully used to replace 50% of the phenol in PF resin.
Key words: adhesive, biomass, tannin, lignin, pyrolysis.
Correspondence: Chia-Ming Chen, School of Forest Resources, The University of Georgia, Athens, GA 30602, USA
Telefax: +1-706-5428356