Isolation of cellulose nanocrystals from grain straws and their use for the preparation of carboxymethyl cellulose-based nanocomposite films

• α-Cellulose content of rice, wheat, and barley straws was 36.9, 43.0, 39.2%, respectively.
• Yield of CNCs were 64, 75, and 69 wt% for cellulose of RS, WS and BS, respectively.
• Width and length of the CNCs were 10–25 and 120–800 nm with aspect ratio of 16–19.
• Tensile strength increased by 45.7%, 25.2% and 42.6% for RS, WS and BS, respectively.
• WVP decreased by 26.3%, 19.1% and 20.4% for RS, WS and BS, respectively.

Cellulose nanocrystals (CNCs) were isolated from rice straw (RS), wheat straw (WS), and barley straw (BS) by using acid hydrolysis method. They were fibrous in shape with length (L) of 120–800 nm and width (W) of 10–25 nm, aspect ratio (L/W) of 18, 16 and 19, crystallinity index (CI) of 0.663, 0.710, and 0.634, and yield of 64, 75, and 69 wt% for RS, WS, and BS respectively. Carboxymethyl cellulose (CMC)/CNC composite films were prepared with various concentration of the CNCs. SEM results showed that the CNCs were evenly distributed in the polymer to form homogeneous films. Mechanical and water vapor barrier properties were varied depending on the type of CNCs and their concentration. Tensile strength (TS) increased by 45.7%, 25.2%, and 42.6%, and the water vapor permeability (WVP) decreased by 26.3%, 19.1%, and 20.4% after forming composite with 5 wt% of CNCs obtained from RS, WS, and BS, respectively.