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Download fileCarbon Fibers from Lignin-Cellulose Precursors: Effect of Stabilization Conditions
journal contribution
posted on 2019-04-10, 00:00 authored by Andreas Bengtsson, Jenny Bengtsson, Maria Sedin, Elisabeth SjöholmThere
is an increasing demand for lightweight composites reinforced
with carbon fibers (CFs). Due to its high availability and carbon
content, kraft lignin has gained attention as a potential low-cost
CF precursor. CFs with promising properties can be made from flexible
dry-jet wet spun precursor fibers (PFs) from blends (70:30) of softwood
kraft lignin and fully bleached softwood kraft pulp. This study focused
on reducing the stabilization time, which is critical in CF manufacturing.
The impact of stabilization conditions on chemical structure, yield,
and mechanical properties was investigated. It was possible to reduce
the oxidative stabilization time of the PFs from about 16 h to less
than 2 h, or even omitting the stabilization step, without fusion
of fibers. The main reactions involved in the stabilization stage
were dehydration and oxidation. The results suggest that the isothermal
stabilization at 250 °C override the importance of having a slow
heating rate. For CFs with a commercial diameter, stabilization of
less than 2 h rendered in tensile modulus 76 GPa and tensile strength
1070 MPa. Impregnation with ammonium dihydrogen phosphate significantly
increased the CF yield, from 31–38 to 46–50 wt %, but
at the expense of the mechanical properties.