Preparation Of Micronized Montmorillonite Suspension And The Properties And Characterization Of Treated Wood

Montmorillonite (MMT) is a crystalline aluminosilicate with a platete morphology. Because of its rich resources and low price, it has been widely used to prepare montmorillonte/polymer nanocomposite to improve the properties of polymer. In order to improve the properties of wood, micronized montmorillonite suspension as a wood modifier was prepared in this study by using the exchangeable cations in MMT, proper dispersion method and compound dispersants in both one-step and two-step methods. It was then used to treat wood through a full-cell process and the X-ray diffractometer (XRD), fourier transform infraredspectroscopy (FTIR), scanning electron microscope with energy dispersive X-ray analysis (SEM-EDXA), differential thermal analysis-thermogravimetric analysis (DTA-TG), Zeta potential analyzer and laser particle instrument were used to analysis and character, and the following results are obtained:(1) The interlayer distance and surface hydrophobicity of organic montmorillonite modified with DDAC was obviously improved. The order of main factors which influence the modification effect of MMT is:addition amount of modification agent> pH value of system>MMT diffraction concentration>reaction time> aging time>reaction temperature. The optimized process is as follows: modification agent:DDAC; addition amount of DDAC:150%; pH value:10; reaction time:2h; aging time:24h; reaction temperature:50℃. By using this modification process, the interlayer distance of organic montmorillonite (OMMT) was enlarged to a maximum of 27.34 (?) with some layers exfoliated totally. Besides, the surface hydrophobicity of OMMT is obviously improved.(2) The stability of OMMT suspension in aqueous solution was greatly improved by using polyvinyl alcohol (PVA) or polyethylene glycol (PEG) dispersants. The optimized parameters vary with the polymer concentrations. (1) at polymer concentrations higher than 1%, PVA is preferred and the parameters are as follows:DDAC concentration:1.4%; PVA concentration:1% or 2%; pH value: 8-10; OMMT concentration:5%. (2) at polymer concentrations lower than 1%, PEG is preferred and the parameters are as follows:DDAC concentration:<0.7%; PEG concentration:0.25% or 0.5%; pH value:8-10; OMMT concentration:2%. The dispersion method in a order of best to worst is:ball milling>mechanical stirring>ultrasonic dispersion.(3) Samples treated with micronized montmorillonte suspension using PVA as dispersant (PVDMW) were characterized and the properties were tested. PVDMW-2 treated with suspension prepared by two step method showed a great amount of large OMMT clusters blocking in wood cell lumen or covering on the surface of wood cell wall without penetrating into the wood cell wall. As a result, the properties of treated wood are not improved significantly. However, PVDMW-1 treated with suspension prepared by the one-step method showed some exfoliated OMMT layers entering into the amorphous region of wood cell wall, which increased the crystallinity of wood and consequently improved the wood properties to some extent including the thermal property, leaching resistance, dimensional stability, surface hardness and compression strength.(4) Samples treated with micronized organic montmorillonite suspension using PEG1000 or PEG8000 as dispersants (PEDMW) were characterized and the properties were tested. In PEDMW-1 samples treated with suspension prepared by one-step method, the small particles or exfoliated layers of OMMT filled the cell lumen or wood cell wall, which was demonstrated in the detected increasing content of Si element in the wood cell wall. OMMT layers formed complex bonds with alcoholic hydroxyl groups in wood cellulouse and hemicelluloses as well as the carboxyl group in lignin through PEG. As a result, the wood crtstallinity was greated increased and the properties including the thermal property, leaching resistance, dimensional stability, surface hardness and compression streangth of PEDMW-1 were improved significantly. The performance of PEDMW-2 treated with suspension prepared by two-step method is similar to that of PVDMW-2. In PEDMW-8 samples treated with suspension dispersed by PEG8000 in one-step method, the OMMT nano-layers could not get into wood cell wall due to the long chains of PEG8000, which also led to relatively low properties of PEDMW-8.