Material pocket dynamic mechanical analysis: a novel tool to study thermal transition in wood fibers plasticized by an ionic liquid (IL)
Abstract The investigation of phase transition in powdered materials by dynamic mechanical analysis (DMA) is not straightforward because powders are difficult to prepare in a solid compact form without altering their structure and properties. In this study, a material pocket (MP) method has been applied to provide physical support to powdered samples for DMA testing (MP-DMA). Poplar wood strips and four types of wood particles [native wood flour (WF), α-cellulose (αC), holocellulose (HC), and particles without hemicelluloses (HR)] were treated with an ionic liquid (IL), 1-ethyl-3-methylimidazolium chloride ([Emim]Cl), to a weight percent gain (WPG) of 36%. Results show that all four [Emim]Cl-treated wood particles exhibited three apparent transition peaks over the measured temperature range. Paracrystalline cellulose, hemicelluloses, and lignin all exhibited a glass transition temperature (Tg) at approximately 85°C due to the plasticizing effect of [Emim]Cl. The transition peak at a higher temperature may be due to the melting of crystalline cellulose in [Emim]Cl. MP-DMA is an effective tool for direct monitoring the phase transition of powdered lignocellulosics. This provides new insight into the interactions of ILs and cell wall polymers, and the method established can be easily extended to other systems based on powdered samples.
