All-cellulose composite and nanocomposite made from partially dissolved micro- and nanofibers of canola straw

Abstract

All-cellulose composite (ACC) and nanocomposite (ACNC) were, respectively, made from microfiber and grinding-based nanofiber of canola straw by using a partial dissolution method with the solvent N,N-dimethylacetamide/lithium chloride (DMAc/LiCl). The dissolution times were 5, 10, 20, 30, 60 and 120 mins. The resultant composites were compared with neat micro-and nanofiber sheets. The average diameter of microfiber was 26 μm, which was downsized to 32 nm after grinding. The grinding process is a simple, cheap and fast downsizing method that could reduce fiber diameter by almost three orders of magnitude. The tensile strength of the nanofiber sheet was 11 times higher than that of the microfiber sheet. As dissolution time increased, the amount of non-crystalline matrix in the ACC and ACNC increased, and the apparent crystallinity decreased. The ACC had a tensile strength of 59 MPa when the dissolution time was 120 min, whereas the ACNC approached a maximum tensile strength of 164 MPa after a short dissolution time (10 min). Fiber pull-out was observed in the tensile-broken surfaces of the micro- and nanofiber sheets, and fibers tended to break when the dissolution time was long. High-performance all-cellulose nanocomposite was made from canola straw as a low-value agricultural residue through a cheap and fast method of downsizing (grinding) followed by a short partial dissolution process (10 min) in N,N-dimethylacetamide/lithium chloride solvent.