Effect of borax-boric acid Treatment of simul (Bombax ceiba) Veneers on Glue-Bond Quality of Plywood
K Akhter, Md Abul Hashem, S Akhter
The glue-bond quality of plywood made of treated simul (Bombax ceiba) veneers was investigated. The veneers were treated with cold and hot water solution of borax-boric acid (BB) of different concentrations and treatment durations. The plywoods were made at three different pressures in hot press using urea formaldehyde glue. The glue-bond strength of untreated plywood in dry shear-test was found to be 2.17 and 2.29 N/mm2 made at 1.05 and 1.40 N/mm2 pressure respectively. It was observed that the values of load at failure of treated plywood in dry shear-test gradually decreased with the increasing treatment duration and concentration of solution.
Comparison of the bond strength of untreated plywood with the treated ones made with urea formaldehyde glue showed that all the treatment combinations lowered the bond quality. It was also found that 10% BB solution and highest treatment duration (3 for cold water days and 60 minutes for hot water) lowered the bond strength of the plywood which met ‘B-grading’ requirement. However, the values of glue bond strength in all other BB treated plywood met ‘A-grading’ requirement for gluing. It may be due to the
highest percentage of chemical deposition within the cell wall structure lowered the bond quality. For all the treatments, low values of shear strength were observed in plywood made of hot water-treated veneer compared to that of cold water.