MONTMORILLONITE NANOPARTICLE DISTRIBUTION AND MORPHOLOGY IN MELAMINE-UREA-FORMALDEHYDE RESIN-IMPREGNATED WOOD NANOCOMPOSITES

Attempts were made to investigate nanoparticle distribution in aspen by using electron probe microanalysis (EPMA) and Wincell software analysis to detect and analyze aluminum elements of impregnated montmorillonite (MMT) nanoclays. The cross-section morphologies of both untreated and nanoclay/melamine-urea-formaldhyde (MUF)-treated wood samples were characterized by transmission electron microscopy (TEM) and atomic force microscopy (AFM). With the combination of EPMA and TEM, it was demonstrated that nanoparticles were distributed through the wood cell wall structure. Wood cell walls functioned as filters or sieves to capture nanoparticles, especially in the compound middle lamella and the external layer of the secondary wall (SI) to form a nanoparticle distribution network. The interphase interaction and adhesion between MMT and MUF resin was characterized by AFM observation. Organophilic montmorillonites showed better interphase interactions than the pristine untreated hydrophilic MMT nanoparticles. It was confirmed that the functional groups on the surface of MMT play an important role in the compatibility between MMT nanoclay and MUF resin, which have a strong influence on the physical/mechanical properties of the resulting nanoclay/MUF wood nanocomposites.