The effect of PF/PVAC weight ratio and ambient temperature on moisture absorption performance of bamboo‐bundle laminated veneer lumber

The veneer preprocessing densification is a vital procedure in the manufacturing process of long‐span bamboo‐based engineering material, bamboo‐bundle laminated veneer lumber (BLVL). The adhesive used in the preprocessing densification process was the mixture of phenol formaldehyde (PF) resin and polyvinyl acetate (PVAC) resin. The objective of this study was to investigate the effect of PF/PVAC weight ratio on the moisture absorption performance of BLVL, as well as the effect of ambient temperature on the hygroscopic swelling performance for BLVLs with a PF/PVAC ratio of 6:1. The results indicated that the water absorption swelling rate and weight gain rate of the BLVLs decreased as PF/PVAC ratio increased at 63°C. The absorption behavior of BLVL was found to obey Fick's law at 63°C approximately. The higher the PF/PVAC ratio, the lower swelling parameter K _SR and D values were obtained. However, PF/PVAC ratio exerted little effect upon the bending properties(modulus of rupture and elasticity) of BLVL. Temperature has a significant effect on the moisture absorption performance of BLVL (6:1 PF/PVAC ratio). The higher the temperature, the greater swelling and weight gain rate was obtained, as well as K _SR and D values. The calculated swelling activation energies ( E _S ) were 25.79 and 22.45 KJ mol ⁻¹ for BLVLs with 6:1 PF/PVAC ratio and the ones with neat PF resin, respectively, while the diffusion activation energies ( E _D ) were 10.62 and 8.47 KJ mol ⁻¹ . POLYM. COMPOS., 37:955–962, 2016. © 2014 Society of Plastics Engineers