蒙脱土/聚乙二醇/超支化聚丙烯酸酯乳液改性木材的力学性能

Mechanical properties of wood modified by montmorillonite/poly(ethyl glycol)/hyperbranched polyacrylate emulsion

【目的】木材化学改性是提高人工林速生材力学性能,延长其使用寿命,扩大其应用范围的有效途径。使用有机蒙脱土(OMMT)对木材进行改性处理具有较好的前景。但由于有机蒙脱土在水中不易分散,且粒径较大,难以进入到木材细胞壁中而限制了其应用。因此,提高OMMT在水中的分散性,增大其层间距可为其进入木材细胞壁内创造条件,是改性增强木材的有效手段。【方法】本研究采用一种水性的聚乙二醇/超支化聚丙烯酸酯乳液(PEG/HBPA)作为载体使OMMT在水中稳定分散。将改性剂通过浸渍处理改性木材,测试了改性材的力学性能,并探讨了不同层间离子的OMMT对改性效果的影响。【结果】4种OMMT均能够稳定分散进入到PEG/HBPA中,经过24 h静置后无明显的分层和沉淀,乳液粒径和黏度无明显变化。木材经过PEG/HBPA处理后,除端面硬度外,力学性能有所提高,加入OMMT后力学性能进一步提高,并增加了改性材的端面硬度。OMMT层间离子中含有氨基、羟基、羧基等官能团,能使OMMT更好地进入到木材细胞壁中,其中层间离子含有氨基的OMMT改性效果较好,改性后木材顺纹抗压强度为82.2 MPa,抗弯强度为98.2 MPa,端面硬度为8920 N。【结论】使用PEG/HBPA乳液可以均匀分散OMMT,并使其进入到木材细胞壁,增强木材的力学强度,这对实现人工速生材的环保高效利用具有一定的指导意义。

[Objective]Chemical modification of wood was an effective way to improve the mechanical properties,prolong the service life,and broaden the application of fast-growing wood.Wood treated with organo-montmorillonite(OMMT)has a good prospect.However,the difficulty of dispersion of organomontmorillonite in water as well as the large particle size limited its application.Therefore,improving the dispersion of OMMT in water,simultaneously enlarging its interlayer distance could create conditions for OMMT to enter into the wood cell walls.And also,it was an effective way for wood modification.[Method]In this study,a kind of waterborne poly(ethyl glycol)/hyperbranched polyacrylate(PEG/HBPA)emulsion was used as carrier to enhance the water stability of OMMT.The wood was modified by impregnation and the mechanical properties were tested.Besides,the different ions in the interlayers of OMMT on the modification effects were investigated.[Result]The four kinds of OMMT all can stably dispersed in PEG/HBPA.After 24 hours of rest,no stratification and precipitation occurred,and the particle size and the viscosity did not obviously change.Wood treated with PEG/HBPA showed improvements on the mechanical properties except for the cross hardness.Incorporation of OMMT can further improve the mechanical properties of wood,and the cross hardness was also improved.OMMT containing amino,hydroxyl and carboxyl groups in its interlayers can be better penetrated into the wood cell walls.Among which,OMMT containing amino groups performed the best.The radial compression strength,flexural strength,and the cross hardness of treated wood reached 82.2 MPa,98.2 MPa and 8920 N,respectively.[Conclusion]Thus,using PEG/HBPA emulsion is an effective way to evenly disperse OMMT.And the OMMT layers can be penetrated into the wood cell walls,improving the mechanical properties,which has a guiding significance on the environmentally friendly and highly-efficient use of fast-growing wood.