Shear Refinement of Formaldehyde-Free Corn Starch and Mimosa Tannin (Acacia mearnsii) Wood Adhesives

Abstract

The aim of this work was to reduce the viscosity of formaldehyde-free corn starch-mimosa tannin wood adhesives, without adversely affecting the mechanical properties of the product. The reduction of viscosity was achieved using shear refinement. The study focused on the physical phenomena before cross-linking of the wood adhesive. The physical (rheological characterization) and mechanical (bond strength) properties of formaldehyde-free corn starch and mimosa tannin wood adhesives were measured.The results showed that the shear refinement (290 rpm and 5 min, optimal conditions) reduced the viscosity of the corn starch-mimosa tannin wood adhesives (from 100 000 to 458 Pa s) with the advantage of being stable over time. Mechanical tests showed that the shear refinement did not influence the mechanical properties of corn starch-mimosa tannin wood adhesives.

Preparation and Properties of Cassava Starch-based Wood Adhesives

“…Several researchers have evaluated the potential utilization of starch (Imam et al 1999(Imam et al , 2001, starch/tannin (Moubarik et al 2009(Moubarik et al , 2010(Moubarik et al , 2011, and starch/isocyanates (Tan et al 2011) as starchbased wood adhesive (SWA). SWA can be prepared by grafting an olefin monomer (VAc or VAc + BA) onto starch granules; the monomer then reacts with the OH group of the glucose unit to produce an ether linkage (Wang et al 2012Zhang et al 2015).…”

Starch: An Undisputed Potential Candidate and Sustainable Resource for the Development of Wood Adhesive

“…Besides, native starch also exhibits high viscosity due to the presence of high molecular weight macromolecules. Thus, addition of small molecule is suitable to decrease the number of entanglements allowing smooth flow and permeation of adhesive onto the wood surface …”

“…Recently, research has been focused to develop adhesive from starch by incorporating replacement or extender to obtain product with low cost and increased viscosity . Corn starch has been explored by adopting starch/isocyanates, starch/tannin, and starch/polyvinyl alcohol systems for the development of adhesives . The properties of adhesive vary greatly depending on the derived sources …”