Enhanced mechanical and hydrophobic properties of composite cassava starch films with stearic acid modified MCC (microcrystalline cellulose)/NCC (nanocellulose) as strength agent

The green composite cassava starch films were prepared using stearic acid modified microcrystalline cellulose (M-MCC)/nanocellulose (M-NCC) as strength agent, which shows good mechanical and hydrophobic properties and is a candidate for food package in this work. Microcrystalline cellulose (MCC) was prepared with 98% phosphoric acid hydrolysis and mechanical stirring at 600 r/min and nanocellulose (NCC) was prepared with 65% sulfuric acid hydrolysis. After using stearic acid to modify MCC and NCC, the casting method was used to prepare the M-MCC/cassava starch composite films and M-NCC/cassava starch films. Physical, mechanical, hydrophobic and thermal properties were characterized using SEM, electronic universal testing machine, contact angle meter and TGA. The results showed that: M-MCC and M-NCC can lead to the enhancement of mechanical and hydrophobic properties of composite films; 0.5% M-MCC and 1.5% M-NCC had the highest enhancement effect on mechanical properties, leading the tensile strength of cassava starch film increased by 484.5% and 327.7% respectively; As to hydrophobic property, when 2% M-MCC and 0.5% M-NCC added, the hydrophobicity of the film increased by 65.0% and 30.3% respectively. Overall, the enhancement effect of M-MCC was better than M-NCC. But when M-MCC/M-NCC was added, the thermal stability of films reduced.