Produção de painéis compensados com adesivos de líquido da casca de castanha de caju à base de cardanol modificado com nanoestruturas de lignina

Abstract

Due to the undesirable effects and degradation of air quality caused by oil-based adhesives, there is interest in developing natural adhesives. Cardanol, derived from cashew nut shell liquid (LCC), is a natural product with potential use in the manufacture of adhesives, due to its chemical constitution and its double bond position, which allows for numerous functionalizations. Furthermore, the addition of lignin nanostructures in the adhesive can enhance the bonding properties. The objective of this work was to analyze the influence of different concentrations of lignin nanostructures on cardanol-formaldehyde adhesive. The panels were glued with Pinus oocarpa blades and 280 g/m² adhesives with the addition of lignin nanostructures at 0, 1, 2 and 3%. The pressing cycle was 1.0 MPa at 160ºC in a hydraulic press and, subsequently, the panels were acclimatized, to then be made of test specimens for the tests. The physical-mechanical tests carried out on the panels were: apparent density, humidity on a dry basis, total water absorption, shearing in the glue line in the condition (dry, wet and post-boiling), flexion test with evaluation of the modulus of elasticity and rupture and combustibility test. Plywood panels produced with cardanol-based cashew nut shell liquid adhesive modified with lignin nanostructures showed superior results in all physical-mechanical tests, except for the parallel MOE and MOR and for total water absorption. For these properties, the addition of lignin nanostructures did not change the values obtained. In all treatments, the shear strength in the glue line with 0% lignin nanostructure was lower and showed statistical difference to the others that were equal to each other. The lowest value was (0.64 MPa) after boiling, with 0% lignin nanostructure, not meeting EN 314-2 of 1993 with a minimum of 1 MPa. The other treatments were higher than 1 MPa. In addition, the results found allow us to state that the lignin nanostructures provided the panels with better flame behavior, making them suitable for use in civil construction.