Effect Of Processing Bamboo Strip On Its Wettability And Bonding Strength

Determining the contact angle of several kinds of wetting liquids on the tangential section of bamboo, which included distilled water, urea-formaldehyde resin adhesive (UF) and phenol formaldehyde resin adhesive (PF), the variation of the dynamic wettability of different culm parts of bamboo (Phyllostachys pubescens) was analyzed, and the difference of wettability between UF and PF was discussed. According to the results above analyses, the bonding strength of the bamboo laminate different structure mats were tested and compared, which were assembled3kinds of bamboo laminate mat structures depended upon varying glued surface of bamboo strip, and glued with same hot-press parameters. And then, the effect treated with hot water, H2O2solution and boric solution on the wettability of UF or PF on the tangential section of bamboo, moreover the change of chemical component was analyzed by FTIR. Finally, in order to avoid from the environment pollution, a mechanic method improving the wettability and bonding strength was put forward, which processed reticulate pattern on tangential section of bamboo. Results of a series of experiments as following:(1) Contact angle of PF or UF on the tangential section of bamboo was less than90degree, so PF or UF could wet on the planning section of bamboo. Their equilibrium contact angle decreased with the increase of the planning depth from the outside to the inside of bamboo wall, on the contrary, the wetting speed raised. However equilibrium contact angle increased slightly and the wetting speed decreased somewhat on the tangential section that was near to the inner skin of bamboo. In addition, heightening the bamboo height from root to top, the equilibrium contact angle of PF or UF on the tangential section planning same depth was smaller, and the wetting speed was quicker. So the wettability on the tangential section planning same depth was better with increasing the culm height.(2) The bonding strength gluing between two sections near the inner skin was the greatest, while gluing between two sections near the outer skin the bonding strength was the worst, and the bonding strength was fell in between the above two structures if gluing between a section near to the outer skin and a section near to inner skin. (3) As different solution treating bamboo strip, effects of the treatment conditions on wettability of the wetting liquids on the tangential section of bamboo were varied, which they were solution concentration, treatment temperature and time.The wettability of distilled water on the tangential section of bamboo treated in the hot water was improved obviously, and the interaction effect between the treatment temperature and the treatment time was significant. And the wettability of UF improved markedly too, but effect of the treatment on the wettability of PF was rather little. The optimum conditions treating bamboo strips with hot water were that the temperature was60℃and the time was6hours. Glued the bamboo strip treated with hot water under these conditions, the bonding strength was increased not only used UF as adhesive but also PF, but the bonding strength used UF as adhesive had more significant increase than PF.Treated with H2O2solution, the wettability of the distilled water on the tangential section of bamboo had been improved evidently. The wettability of the UF on the tangential section improved with increasing the treatment temperature and prolonging the treatment time, when the concentration of H2O2was low and the treated bamboo strips were washed or soaked clearly with water. However, the wettability of the PF on the tangential section of bamboo treated with H2O2solution became worse slightly. The optimum conditions treating bamboo strip with H2O2solution were:the H2O2concentration is2%, treatment temperature is70℃and the treatment time is6hours. The bonding strength glued the bamboo strips used UF as adhesive was enhanced, which were treated with H2O2solution under these conditions, on the contrast, the bonding strength glued with PF decreased slightly.On the tangential section of bamboo treated with boric acid solution, the wettability of the distilled water became worse with increasing the concentration of the boric acid solution, while it was improved distinctly as increasing the treatment temperature and prolonging the time. The wettability of UF was improved with the increase of the boric acid solution concentration and prolonging the treatment time, but it was the best when the treatment temperature was60℃. And the wettability of PF was meliorated increasing the solution concentration, but it got worse because rising the temperature or prolonging the treatment time. The optimum conditions to treat bamboo strip with boric acid solution for meliorating the wettability were that the concentrate was15%, the treatment temperature was60℃, and the time was6hours. The bonding strength glued the bamboo strips treated with boric acid solution under these optimum conditions got worse, not only used UF as adhesive but also PF.(4) The wettability of PF or UF adhesive on the tangential processed reticulate pattern on the tangential section of bamboo was improved, moreover the wettability got better when the net mesh was20and the specific pressure was6MPa. In addition, the bonding strength of the bamboo strip was strengthened obviously whether UF or PF as adhesive.