Sequential Fractionation of Cottonseed Meal to Improve Its Wood Adhesive Properties

Abstract

AbstractFor better understanding of the adhesive properties of different fractions of cottonseed protein, cottonseed meals from both glanded and glandless cotton varieties were separated into several fractions. Each meal was sequentially extracted with water and 1 M NaCl solution, or with phosphate buffer and NaCl solution. Adhesives were prepared from the recovered fractions and hot‐pressed onto maple veneer strips and tested for their properties. The adhesive strength of the water‐ and buffer‐washed solid fractions (i.e., the un‐extractable residues of the meals) from the glanded seed ranged from 1.32 to 1.62 MPa and were unchanged or increased compared with the adhesive strength of the original meal that varied from 0.98 and 1.49 MPa. Soaking the wood specimens bonded at 80 °C revealed that the water resistance of these water‐ and buffer‐washed adhesives was significantly improved in that they exhibited no delamination during soaking compared with the meal adhesive that showed some delamination (20–30 % of the samples). Furthermore, the water resistance of these fractions with wet shear strength around 1.5 MPa was comparable to that of cottonseed protein isolate (>90 % protein) when the joints were bonded at 100 °C. The preparations from glandless cottonseed meals showed similar adhesive performances. Additional extraction of the meals with NaCl solution reduced adhesive performance. The results suggest that water‐ or buffer‐washed cottonseed meal fractions can be used as wood adhesives and would be less costly to prepare than cottonseed protein isolates.