Preparation And Properties Of Cassave Residue Nanocellulose/cassave Starch Composite Films

Cassava residue is a waste of industrial production of starch and ethanol.A large amount of cassava residue is directly buried or discarded every year in China,which not only causes waste of resources,but also pollutes the environment.The cassava residue has a high cellulose content and is a natural cellulose raw material.If it can be effectively utilized,the commercial value of cassava residue will be greatly improved.In this paper,nanocellulose was prepared from cassava residue by high pressure homogenization method,and then four kinds of modified nanocellulose were prepared.The cassava residue,nanocellulose and modified nanocellulose were characterized by scanning electron microscopy,transmission electron microscopy,atomic force microscopy,infrared spectroscopy,X-ray difSractometry,thermal stability analysis and X-ray photoelectron spectroscopy.The effect of CNF and modified CNF on the performance of cassava starch-based nanocomposite film was investigated by using cassava starch as the film-forming substrate.In this paper,nanocellulose was prepared from cassava residue.After enzymatic hydrolysis and bleaching,the cellulose content increased from 20.21%to 77.39%,the starch content decreased from 50.39%to 1.87%,the hemicellulose content decreased from 18.38%to 5.11%,and the lignin content decreased from 3.69%to 0.74%.The cassava residue fibers were homogenized at 15,000 psi for 30 times and successfully prepared nanocellulose,and the diameter of CNF was about 10 nm.Compared with cassava residue,the thermal stability of CNF was improved,and the crystallinity index of CNF increased from 18.61%to 57.51%.However,amylase treatment,bleaching and high pressure homogenization did not change the crystal structure of cassava residue fiber,and it was still cellulose I structure.In order to improve the hydrophobicity of CNF and the dispersibility in water,CNF was modified with silane coupling agent KH-550 and L-malic acid respectively to prepare silane coupling agent KH550 modified nanocellulose(J-CNF),L-malic acid modified nanocellulose(Z-CNF),L-malic acid modified J-CNF(J-Z-CNF)and silane coupling agent KH550 modified Z-CNF(Z-J-CNF).Compared with CNF,the dispersion of the four modified CNF was significantly better,with the diameter of Z-CNF decreasing and J-CNF increasing.The modification did not significantly reduce the crystallinity of nanocellulose,nor did the crystal structure of nanocellulose change.Among the four modified nanocelluloses,the contact angle of Z-CNF is the largest and the thermal stability of Z-J-CNF is the best.The addition of CNF and modified CNF can greatly improve the tensile strength of the cassava starch-based nanocomposite film,and the hydrophobicity and barrier property were also improved,but the elongation at break and the light transmittance of the film were lowered,and the surface roughness of the film was increased.Compared to pure cassava starch film,the water vapor permeability of 3%CNF/TPS,3%Z-CNF/TPS and 3%Z-J-CNF/TPS composite films decreased by 25.68%,35.05%and 35.95%,respectively,and the oil permeability decreased by 40.66%,46.15%and 49.45%,respectively.Z-CNF/TPS and Z-J-CNF/TPS composite films have higher tensile strength and light transmittance,better barrier properties,lower water absorption and water solubility,and larger contact angle than CNF/TPS composite films.