STRUCTURAL PLYWOOD MANUFACTURED WITH POLYURETHANE ADHESIVE BASED ON CASTOR-OIL: AN EXPERIMENTAL STUDY

摘要

Internationally, a lot of efforts have been made in order to find alternative materials to manufacture wood based products. Among these products, structural plywood can be mentioned. Usually, structural plywood is produced with some kinds of adhesive that can cause significant environment and human health hazards. In Brazil, research about alternative adhesives has been initiated in trying to eliminate or reduce the mentioned undesirable problems. In this paper, an experimental study about structural plywood manufactured with polyurethane adhesive based on castor oil (PACO) is presented. Castor oil (Ricinus communis) is a natural and renewable resource, widely available in several Brazilian regions. Researchers of the Sao Carlos Chemical Institute, Sao Paulo University (USP), originally produced this adhesive. Some structural applications of PACO have already been studied in Wood and Timber Structures Laboratory (LaMEM), Engineering Structures Department (SET) in Sao Carlos Engineering School (EESQ, USP, showing very interesting results, as example, in glued laminated timber members. The present study involves the production of plywood with 15-mm thickness, using five 3-mm plies obtained from Eucalipto Grandis (Eucalyptus grandis) and Eucalipto Urophylla (Eucalyptus urophylla) trees. The plywood performance was evaluated by mechanical tests conducted in accordance with recommendations of the normative documents NBR 9533/86 - Plywood: determination of static bending properties; and NBR 9534/86 - Plywood: determination of shear strength of glue line, both edited by Brazilian Technical Standards Association (ABNT). The results indicate that PACO is a very satisfactory alternative adhesive in producing structural plywood.