Author : Surdiding R. Warsa

Summary : Sweet potato and cassava flours were tried as extenders for urea and phenol formaldehyde adhesives. Properties of the adhesives were compared with those extended with wheat flour, a common extender in synthetic resin adhesives used to reduce its glueline costs. Kalumpit (Terminalia microcarpa Decne), a Kesser known species, was used as the substrate in this study. A 3 x 5 factorial experiment in completely randomized design with 5 replicates was employed. The factors were type of level of extender. The type of extender had three levels namely: sweet potato, cassava, and wheat flours. The extender had five levels namely: 10, 20, 30, 40, and 50 percent of resin solid of neat adhesive. Urea formaldehyde adhesive extended with sweet potato flour developed good gluebond quality. However, it was lower than that extended with either cassava or wheat flour. Extension can be done up to either 30 percent of sweet potato or 20 percent of cassava flour produced which a depression of gluebond quality will be relatively small. Phenol formaldehyde adhesive extended with sweet potato flour reduced plywood with good bond quality. The value was higher than the one extended with cassava flour, and was lower that extended with wheat flour. The proposed levels of extension are 40 percent and 30 percent for sweet potato and cassava flour, respectively. Plywood glued with either urea or phenolic resin complied with the gluebond requirements of PHILSA Standard Specification for Plywood for interior and exterior types of bond. Most dry specimens were broken in tension, particularly those glued by phenolic resin in which longer pressing time was used. Kalumpit produced good plywood either glued by urea or by phenolic resins with an average value of shear strength of 179 psi and 191 psi, respectively.