Thursday 13 December 2012

Cellulose Nanofibre Nonwoven Fabrics

Satoru Yoshida of Asahi Kasei Fibers Corp., Moriyama City (Japan) has produced nanofibres by refining woodpulp into the 30 to 100 nm fibril range and producing wet-laid sheets down to 3 gsm with comparable surface area and porosity to electrospun nanofibres.  The sheets also show unusually high heat stability (better than hydrophilic PTFE film) and a usefully lower coefficient of thermal expansion than cellophane film.

The manufacturing process for CNF involves conventional beating of wood pulp to a highly fibrillated state, followed by high pressure homogenisation of the resulting slurry. From the micrographs, this completely destroys any residual fibre backbones to yield an all-fibril dispersion – “Micro-Fibrillated Cellulose”.

Applications developed so far include a transparent hybrid epoxy/CNF film with high transparency and low thermal expansion (50-200C), and functional filters where the surface of the CNF is chemically modified, e.g. crosslinked to improve wet strength.  Battery separators and capacitor dielectrics were mentioned as end-products.

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