Gluability and formaldehyde-emission in yemane (Gmelina arborea R.Br.) plywood using giant ipil-ipil (Leucaena leucocephala (Lam.) de wit) seed flour as glue extender

Giant ipil-ipil seed flour had higher ash, crude protein, crude fat and crude fiber contents than wheat flour. The high amounts of crude protein, crude fat and crude fiber did not pose problems on the spreadability and water-taking capacity of giant ipil-ipil seed flour as extender. The water-taking capacity of giant ipil-ipil seed flour was comparable to wheat flour. Plywood samples bonded with glue mixes extended with giant ipil-ipil seed flour had significantly higher wet shear strength and wood failure compared to wheat flour extended glue mixes. Those results show that glue mixes extended with giant ipil-ipil seed flour is more water resistant compared to glue mixes extended with wheat flour. At 15.89 and 31.78% glue extension, a shorter pressing time could be applied in glue mixes extended with giant ipil-ipil seed flour, compared to wheat flour. The shear strength retention of plywood samples bonded with glue mixes extended with giant ipil-ipil seed flour was significantly higher (69.80%) than those glued with wheat flour extended glue mixes (63.42%). A maximum of 47.66% glue extension could be used for both types of extender to obtain acceptable bond shear strength and wood failure. Giant ipil-ipil seed flour controls formaldehyde emission in plywood samples better than wheat flour. Both pressing time and level of extension significantly affected the formaldehyde release in plywood samples. The increase in pressing time and level of glue extension decreased the amount of formaldehyde release. The lowest formaldehyde emission of 2.28 ug/ml was obtained at the highest level of giant ipil-ipil seed flour glue extension (74.44%) and at 4 minutes pressing time. The superior performance of glue mixes extended with giant ipil-ipil seed flour could be attributed to its higher protein content which made it more water resistant than wheat flour and more reactive with formaldehyde, thus reducing formaldehyde release.