Strong and optically transparent films prepared using cellulosic solid residue recovered from cellulose nanocrystals production waste stream.

We used a new cellulosic material, cellulosic solid residue (CSR), to produce cellulose nanofibrils (CNF) for potential high value applications. Cellulose nanofibrils (CNF) were produced from CSR recovered from the hydrolysates (waste stream) of acid hydrolysis of a bleached Eucalyptus kraft pulp (BEP) to produce nanocrystals (CNC). Acid hydrolysis greatly facilitated homogenization to fibrillate CSR to CNF with only 15 passes in a microfluidizer compared with at least 47 passes to fibrillate BEP to nanofibrils. CNF from CSR were nanowhiskers with a length between 50 and 400 nm and a diameter 3-10 nm with limited aggregation while CNF from BEP were entangled networks of nanofibrils with a length of 500-1000 nm and a diameter of 10-50 nm. CNFs from CSR had good spectral transparency from UV to infrared, i.e, transmittance of CNF-CSR suspensions at 0.1% solids consistency is greater than 90% at wavelengths greater than 340 nm, compared with less than 30% for CNF suspension produced from BEP. Specific tensile strength and modulus of CNF films from CSRs reached 75 kN·m/kg and 12 MN·m/kg, respectively, approximately 175% of the respective values for conventional paper made of refined BEP.