Castor oil polyurethane adhesive for glulam

Transcription

1 Castor oil polyurethane adhesive for glulam Jesus, Jose M. H 1., Calil Jr, Carlito 2, Chierice, Gilberto O. 3 INTRODUCTION Researches have been taken place in Laboratory of Wood and Timber Structures (LaMEM) of School of Engineering São Carlos of São Paulo University, in order to develop new natural adhesives with mechanical strength and humidity resistance. A work of Ph.D. thesis (JESUS, 1) is in development at USP / São Carlos with the aim to analyze the behaviour of the polyurethane adhesive based on castor oil to used in glulam. The most important reasons to this study are: to be a Brazilian technology developed by national researchers in the Laboratory of Analytic Chemistry and Polymer Technology, of the Institute of Chemistry of São Carlos, USP; to be made of a renewable resource without any organic solvent, biodegraded and not aggressive both to the man and to the environment and to have lower cost than the commercial adhesive employed. OBJECTIVES The aim of this work is the determination of mechanical properties of study of the behaviour of polyurethane adhesive based on castor oil resin in order to use in glued laminate timber beams. MATERIALS AND METHODS The efficiency of the adhesive was evaluated through shear tests in adhesive line. The wood species Pinus caribea hondurensis and Eucalyptus grandis were chosen because are used as reforestation in the South and Southeast areas of Brazil and in the production of glulam by the local industries. The adhesive studied is two components type, composed by the poliol 040 and the prepolymer 24 and environment conditions cure. The statistics design employed in this experimentation was the factorial design at three levels. The shear tests took place following the Brazilian Code NBR 710: Design of Timber Structures,, in order to evaluation some factors that influence the adhesion process. These factors are the gluing pressure, the time of pressure and the viscosity of the adhesive through the control of the time elapsed between the mixture of the components of the adhesive and its spread on the wood surfaces, looking for the best values of strength. Each one had three factorial levels. These factors had its levels combined three to three and all the combinations were testing with three samples, besides to test massive specimens used as test controls. Three levels of gluing pressure were adopted (0.4, 0.6 and 0.8 MPa) and three times of pressure (4, 6 and 8 hours). For the viscosity the levels (t) adopted were 0, 3 and 6 minutes. The time of cure used in the tests was 8 days. When the best combination of parameters were determined, news tests were made using the best combination in order to determine the best cure time. The levels of the curing time were 4, 8,, and 20 days. The tests were conducted in environmental conditions and in the moisture content (%). RESULTS The average values for the Pinus caribea hondurensis are showed in the figures 1, 2, 3 and 4. Figure 1 shows that the best combination of parameters for the gluing pressure of 0.4 MPa occurred with the viscosity corresponding to the time t=3' and the time of pressure of 4 hours. The value of the shear strength in the glue line was.07 MPa. Figure 2 1 Asst. Professor, Federal University of Mato Grosso, henrique@sc.usp.br 2 Professor, São Paulo University, calil@sc.usp.br 3 Professor, São Paulo University, gchierice@sc.usp.br

2 shows that the best combination of parameters for the gluing pressure of 0.6 MPa occurred with the viscosity corresponding to the time t=6' and the time of pressure for 4 hours. The value of the shear strength in the glue line was.46 MPa. Figure 3 shows that the best combination of parameters for the gluing pressure of 0.8 MPa occurred with the viscosity corresponding to the time t=0' and the time of pressure of 4 hours. The value of the shear strength in the glue line was.0 MPa. The average value shear strength of the massive specimen used as test control was.74 MPa. Figure 4 shows the days as the time of cure.,6,4,2.4 f gv,0,8,6,4,2,0,8 =.74 MPa Figure 1 Gluing pressure of 0.4 Mpa,0,5,5,0,5,0 8,5 8,0 7,5 7,0 Viscosity: t=0' t=3' t=6' =.74 MPa.46 Figure 2 Gluing pressure of 0.6 MPa.

3 ,8,6,4,2,0,8,6,4,2,0 8,8 8,6 8,4 8,2 8,0.0 =.74 MPa Figure 3 Gluing pressure of 0.8 MPa Strength Shear strength, Time of cure (days) Figure 4 Time of cure The average values for the Eucaliptus grandis are showed in the figures 5, 6, 7 and 8. Figure 5 shows that the best combination of parameters for the gluing pressure of 0.4 MPa occurred with the viscosity corresponding to the time t=3' and the time of pressure of 6 hours. The value of the shear strength in the glue line was.65 MPa. Figure 6 shows that the best combination of parameters for the gluing pressure of 0.6 MPa occurred with the viscosity corresponding to the time t=0' and the time of pressure of 4 hours. The value of the shear strength in the glue line was.70 MPa. Figure 7 shows that the best combination of parameters for the gluing pressure of 0.8 MPa occurred with the viscosity corresponding to the time t=0' and the time of pressure for 4 hours. The value of the shear strength in the glue line was.5 MPa. The average value shear strength of the massive specimen used, as control was.1 MPa. Figure 4 shows the 8 days as the time of cure.

4 f gv, =.1 MPa.65 Average shear strength massive specimem Figure 5 Gluing pressure of 0.4 MPa.,0,5,0,5,0,5,0,5,0,5,0,5,0,5.70 Viscosity: t=0' t=3' t=6' =,1 MPa Figure 6 Gluing pressure of 0.6 MPa. 1.5 =.1 MPa Figure 7 Gluing pressure of 0.8 MPa

5 20 Shear strength Strength Time of cure (days) Figure 8 Time of cure. CONCLUSIONS The best combination of the Pinus caribea hondurensis occurred with the viscosity corresponding to the time t=3, time of pressure of 4 hours and gluing pressure of 0,4 MPa. For the Eucaliptus grandis, the best combination occurred with the viscosity corresponding to the time t=0, time of pressure of 4 hours and gluing pressure of 0.6. The time of cure was 4 days. With 4 days of time of cure the Pinus shear strength (.71 MPa) represents 88.% of the maximum shear strength that is. MPa at days. With 4 days of time of cure the Eucaliptus shear strength (.3 MPa) represents 88.77% of the maximum shear strength that is.44 MPa at 8 days. If one consider that the time of production, transportation and assemble of the structure is higher than 8 or days, 4 days is a very good cure time to adopt for both wood species. The values of the best parameters of these species are higher than massive shear test strength what means that the polymer based on castor oil increase the wood strength. REFERENCES JESUS, J.M.H. Polyurethane Adhesive Study Based On Castor Oil To Glulam, Ph.D. Thesis in development in Laboratory of Wood and Timber Structures- LaMEM, School of Engineering of São Carlos, University of São Paulo - USP, São Carlos SP. (In Portuguese) BRAZILIAN CODE NBR710 Design of timber structures. ABNT,. (In Portuguese)