The distribution and role of nanoclay in lignocellulose-polymer blends

Lignocellulose-polymer blends (LCPBs), particularly those manufactured from wood biomass and recycled plastics, have gained significance as a green alternative to concrete and wood. In the present work, we investigate the mechanisms as to how nanoclay additives improve water-sorption resistance and durability in LCPBs. The microstructure of our extruded and molded clay-redcedar-polyethylene blends are imaged by micro-computed tomography (μ-CT), a promising technique for the characterization of composites. This recent and powerful 3D micro-imaging technique allows noninvasive revelation of the macroscopic to microscopic interactions between different components in a composite. Specifically, our μ-CT study reveals the smearing of clay nanoplatelets over the lignocellulose domains with partial impregnation into the lignocellulose void network. The μ-CT images also suggest partial disintegration of wood cellular structure in clay-added LCPBs. We attribute this modification to penetration of organocations from clay to lignocellulose, as validated by vibrational spectroscopy. To gain further insight, we also monitor the water-sorption kinetics. The kinetics revalidates the well-established role of clay in impeding water's diffusion. In addition, our analysis of the kinetics reveals a novel role of clay in water-sorption resistance. The clay, smeared over hygroscopic lignocellulose particles serves as a sealant and blocks the entry of water. We report nanoclay's role as a sealant for hygroscopic wood particles in hindering water penetration. This sealing attribute of nanoclay is different from its well-established role as a diffusion impeder by torturous paths for the penetrant.