The ultimate quality and performance of fiber/nano-filler composites depends strongly on the interfacial interaction of the components. In particular, the surface energy and surface area of natural nano fibers are directly related to the compatibility, dispersibility, and reinforcement quality. To enhance the adhesion properties at the interface, fibers are often exposed to various surface treatments. In this presentation, surface areas and energies of natural fibers from different origins and surface treatments have been investigated by Inverse Gas Chromatography (IGC).
In our previous study, the surface energies of untreated and oxidized carbon nanotubes (MWCN) and nano-clays and the polyurethane were measured individually by SEA system. The thermodynamic work of cohesion and adhesion were calculated from the surface energy components, which have shown linear relationship with the mechanical properties of the composites, the results are listed in Table 1. The effectiveness of an additive and a matrix combination can be predictable from the work of cohesion and adhesion values based on the
surface energy values of the individual components.
In one of our most recent study in collaboration with Deakin University, the surface energy and the acid-base properties of ultrafine silk powders as new lightweight composite filler was measured by SEA system and the surface energy values were correlated with the cohesiveness and flow ability of the silk powders .
In other recent studies on fibres, the BET surface area values of natural fibers were measured in triplicate to establish the reproducibility of the measurements resulting in standard deviations between 0.1 to 3.5%. Flax fibers had a higher surface area value compared to kenaf and cellulose, which was attributed to the fiber surface roughness . Flax fiber has also higher dispersive surface energy (γd) compared with kenaf and hemp. Additional, decreasing γd for fibers with higher lignin and hemicellulose content was observed . The surface energy values of nano-celluloses can be related to the crystallinity of the fiber due to nano-celluloses with high crystallinities has higher surface energy values .
The inverse gas chromatography technique like SEA is a powerful technique to determine different physicochemical properties of different solid materials which are critical variables for manufacturing processes and product development. This presentation will summarize recent studies where IGC has been used to investigate surface modification of filler materials and its correlation to adhesion phenomena.
Table 1: Thermodynamic works of cohesion and adhesion values and mechanical performances of composites
Figure 1. a) Profiles of surface energies and b) compressibility of silk powders