Study On The Modification Of Bamboo Based On Quaternized Micro-nano SiO₂

In this paper, quaternized micro-nano SiO2 was prepared by the quaternary ammonium salt groups loaded on nano SiO2 and used for the modification of PF, bamboo and its products. The properties of the modified bamboo, such as decay resistance, mildew resistance, bonding strength, hydrophobic, thermal stability, mechanical properties, were evaluated through a variety of experimental methods.(1)Two kinds of quaternized micro-nano SiO2 were synthesized, namely QASN-1 and QASN-2. NMR spectra and infrared spectra confirmed the formation of the quaternized micro-nano SiO2.The Zeta potential value of nano SiO2 changed from negative to positive after surface modification, because the positively charged quaternary ammonium groups were loaded on the surface. Particle size test results showed that the dispersion of QASN-1 in the solvent was the best, followed by QASN-2, nano SiO2 was the worst.(2)Inhibition circle test showed that quaternized micro-nano SiO2 had the best inhibitory effect on Gloeophyllum trabeum, followed by Penicillium citrinum, Fusarium verticillioides, Alternaria alternate spp and Trichoderma viride, Coriolus versicolor, had the worst inhibitory effect on Botryodiplodia theobromae and Aspergillus niger. The quaternized micro-nano SiO2 were further used to treat bamboo samples. The results indicated that QASN-1 had the best inhibitory effect on Fusarium verticillioides, and QASN-2 has the best inhibitory effect on Penicillium citrinum. Anti-sapstain & mildew efficacy of bamboo-bundle laminated veneer lumber(BLVL) with the addition of quaternized micro-nano SiO2 were studied. The results indicated that it had inhibitory effect on Penicillium citrinum on the early stage; and the antibacterial effect on Fusarium verticillioides maintained relatively long. The result of laboratory test indicated that the resistant of modified bamboo to brown rot is higher than white rot. The anti-decay level of modified bamboo at the experimental concentration on white rot is strong. When the concentration were 5%, the anti-decay level of bamboo treated by QASN-1 and QASN-2 to brown rot were strong and a little, respectively. Compared with QASN-2, QASN-1 had a stronger antibacterial ability, because its particle size was smaller than the former, and the net charge was larger than the former.(3)The ESEM images showed that the nanoparticles was uniformly distributed in all parts of the bamboo with sizes between 40~50nm. The contact angle of modified bamboo specimen were 90°~140°. The modification effect on the inner surface of bamboo was better than that on the outer surface, because the issue of the inner face was looser than that of the outer. The inner face absorbed more amount of modifier. The hydrophobicity of bamboo surface modified by QASN-1 was slightly stronger than that of bamboo surface modified by QASN-2. The contact angle measurements demonstrated that the surface of modified BLVL changed from hydrophilic to hydrophobic. The modification effect on bamboo was better than that on BLVL. For the combination of two factors constituted the hydrophobic surface modification of bamboo. One was the silane provided the surface with low surface energy,the other was the nano SiO2 form nanometer rough structure on bamboo surface.(4)The infrared spectrum showed that the cured products of modified PF had the Si-O covalent bond, thus resulting in more stable cured products. The TGA analysis results showed that in the different stages of thermal decomposition, the fast weight loss temperature of modified PF increased about 5~30℃, the weight loss rate of modified PF decreased at 800℃. The bond interface of modified bamboo specimen were studied by environmental scanning electron microscope and fluorescence microscope. The results showed that the penetration depth of the modified adhesive interface decreased slightly. The deteriorating influence of modification of QASN-1 on the mechanical properties of BLVL was relatively more obvious than QASN-2. However, the modification by QASN-1 in turn improved the mechanical of sample when it was impregnated with phenolic resin in advance. The modification reduced the mechanical of sample when it was carried out before sample was impregnated with phenolic resin. This is due to the better hydrophobicity of QASN-1 which would affect the adhesive penetration of BLVL. Therefore, the order of sample modification and impregnation is critical.(5)The modified bamboo powder was also studied by IR spectra and TGA. The results showed that the Si-O-Si covalent bond was formed between the hydroxyl group of bamboo and nano SiO2. The pyrolysis initial temperature of modified bamboo powder was 13~25℃ higher than that of the unmodified bamboo powder.The pyrolysis peak temperature of modified bamboo powder was 15~20℃ higher than that of the unmodified bamboo powder, which indicated that the modification inhibited the thermal decomposition of bamboo powder. The quaternized micro-nano SiO2 increased char yield in the late stage of thermal decomposition. The HRR of modified bamboo was slightly lower than that of untreated bamboo. Compared with that of untreated bamboo, the appearance time of pkHRR of modified bamboo was 15~40s later. The HRR and pkHRR of modified BLVL were lower than that of untreated one. The results showed that the quaternized micro-nano SiO2 had certain flame retardant effect on bamboo and BLVL.